ruby-marc users, a question.

I am working on some Marc8 to UTF-8 conversion for ruby-marc.

Sometimes, what appears to be an illegal byte will appear in the Marc8 
input, and it can not be converted to UTF8.

The software will support two alternatives when this happens: 1) Raising 
an exception. 2) Replacing the illegal byte with a replacement char 
and/or omitting it.

I feel like most of the time, users are going to want #2.  I know that's 
what I'm going to want nearly all the time.

Yet, still, I am feeling uncertain whether that should be the default. 
Which should be the default behavior, #1 or #2?  If most people most of 
the time are going to want #2 (is this true?), then should that be the 
default behavior?   Or should #1 still be the default behavior, because 
by default bad input should raise, not be silently recovered from, even 
though most people most of the time won't want that, heh.