There are plenty of non-free API's, that need some kind of access 
control. A different side discussion is what forms of access control are 
the least barrier to developers while still being secure (a lot of 
services mess this up in both directions!).

However, there are also some free API's whcih still require API keys, 
perhaps because the owners want to track usage or throttle usage or what 
have you.

Sometimes you need to do that too, and you need to restrict access, so 
be it. But it is probably worth recognizing that you are sometimes 
adding barriers to succesful client development here -- it seems like a 
trivial barrier from the perspective of the developers of the service, 
because they use the service so often. But to a client developer working 
with a dozen different API's, the extra burden to get and deal with the 
API key and the access control mechanism can be non-trivial.

I think the best compromise is what Google ends up doing with many of 
their APIs. Allow access without an API key, but with a fairly minimal 
number of accesses-per-time-period allowed (couple hundred a day, is 
what I think google often does). This allows the developer to evaluate 
the api, explore/debug the api in the browser, and write automated tests 
against the api, without worrying about api keys. But still requires an 
api key for 'real' use, so the host can do what tracking or throttling 
they want.

Jonathan

On 12/2/13 12:18 PM, Ross Singer wrote:
> I'm not going to defend API keys, but not all APIs are open or free.  You
> need to have *some* way to track usage.
>
> There may be alternative ways to implement that, but you can't just hand
> wave away the rather large use case for API keys.
>
> -Ross.
>
>
> On Mon, Dec 2, 2013 at 12:15 PM, Kevin Ford <[log in to unmask]> wrote:
>
>> Though I have some quibbles with Seth's post, I think it's worth drawing
>> attention to his repeatedly calling out API keys as a very significant
>> barrier to use, or at least entry.  Most of the posts here have given
>> little attention to the issue API keys present.  I can say that I have
>> quite often looked elsewhere or simply stopped pursuing my idea the moment
>> I discovered an API key was mandatory.
>>
>> As for the presumed difficulty with implementing content negotiation (and,
>> especially, caching on top), it seems that if you can implement an entire
>> system to manage assignment of and access by API key, then I do not
>> understand how content negotiation and caching are significantly "harder to
>> implement."
>>
>> In any event, APIs and content negotiation are not mutually exclusive. One
>> should be able to use the HTTP URI to access multiple representations of
>> the resource without recourse to a custom API.
>>
>> Yours,
>> Kevin
>>
>>
>>
>>
>>
>> On 11/29/2013 02:44 PM, Robert Sanderson wrote:
>>
>>> (posted in the comments on the blog and reposted here for further
>>> discussion, if interest)
>>>
>>>
>>> While I couldn't agree more with the post's starting point -- URIs
>>> identify
>>> (concepts) and use HTTP as your API -- I couldn't disagree more with the
>>> "use content negotiation" conclusion.
>>>
>>> I'm with Dan Cohen in his comment regarding using different URIs for
>>> different representations for several reasons below.
>>>
>>> It's harder to implement Content Negotiation than your own API, because
>>> you
>>> get to define your own API whereas you have to follow someone else's rules
>>> when you implement conneg.  You can't get your own API wrong.  I agree
>>> with
>>> Ruben that HTTP is better than rolling your own proprietary API, we
>>> disagree that conneg is the correct solution.  The choice is between
>>> conneg
>>> or regular HTTP, not conneg or a proprietary API.
>>>
>>> Secondly, you need to look at the HTTP headers and parse quite a complex
>>> structure to determine what is being requested.  You can't just put a file
>>> in the file system, unlike with separate URIs for distinct representations
>>> where it just works, instead you need server side processing.  This also
>>> makes it much harder to cache the responses, as the cache needs to
>>> determine whether or not the representation has changed -- the cache also
>>> needs to parse the headers rather than just comparing URI and content.
>>>   For
>>> large scale systems like DPLA and Europeana, caching is essential for
>>> quality of service.
>>>
>>> How do you find our which formats are supported by conneg? By reading the
>>> documentation. Which could just say "add .json on the end". The Vary
>>> header
>>> tells you that negotiation in the format dimension is possible, just not
>>> what to do to actually get anything back. There isn't a way to find this
>>> out from HTTP automatically,so now you need to read both the site's docs
>>> AND the HTTP docs.  APIs can, on the other hand, do this.  Consider
>>> OAI-PMH's ListMetadataFormats and SRU's Explain response.
>>>
>>> Instead you can have a separate URI for each representation and link them
>>> with Link headers, or just a simple rule like add '.json' on the end. No
>>> need for complicated content negotiation at all.  Link headers can be
>>> added
>>> with a simple apache configuration rule, and as they're static are easy to
>>> cache. So the server side is easy, and the client side is trivial.
>>>    Compared to being difficult at both ends with content negotiation.
>>>
>>> It can be useful to make statements about the different representations,
>>> and especially if you need to annotate the structure or content.  Or share
>>> it -- you can't email someone a link that includes the right Accept
>>> headers
>>> to send -- as in the post, you need to send them a command line like curl
>>> with -H.
>>>
>>> An experiment for fans of content negotiation: Have both .json and 302
>>> style conneg from your original URI to that .json file. Advertise both.
>>> See
>>> how many people do the conneg. If it's non-zero, I'll be extremely
>>> surprised.
>>>
>>> And a challenge: Even with libraries there's still complexity to figuring
>>> out how and what to serve. Find me sites that correctly implement * based
>>> fallbacks. Or even process q values. I'll bet I can find 10 that do
>>> content
>>> negotiation wrong, for every 1 that does it correctly.  I'll start:
>>> dx.doi.org touts its content negotiation for metadata, yet doesn't
>>> implement q values or *s. You have to go to the documentation to figure
>>> out
>>> what Accept headers it will do string equality tests against.
>>>
>>> Rob
>>>
>>>
>>>
>>> On Fri, Nov 29, 2013 at 6:24 AM, Seth van Hooland <[log in to unmask]>
>>> wrote:
>>>
>>>>
>>>> Dear all,
>>>>
>>>> I guess some of you will be interested in the blogpost of my colleague
>>>>
>>> and co-author Ruben regarding the misunderstandings on the use and abuse
>>> of
>>> APIs in a digital libraries context, including a description of both good
>>> and bad practices from Europeana, DPLA and the Cooper Hewitt museum:
>>>
>>>>
>>>> http://ruben.verborgh.org/blog/2013/11/29/the-lie-of-the-api/
>>>>
>>>> Kind regards,
>>>>
>>>> Seth van Hooland
>>>> Président du Master en Sciences et Technologies de l'Information et de la
>>>>
>>> Communication (MaSTIC)
>>>
>>>> Université Libre de Bruxelles
>>>> Av. F.D. Roosevelt, 50 CP 123  | 1050 Bruxelles
>>>> http://homepages.ulb.ac.be/~svhoolan/
>>>> http://twitter.com/#!/sethvanhooland
>>>> http://mastic.ulb.ac.be
>>>> 0032 2 650 4765
>>>> Office: DC11.102
>>>>
>>>
>
>