In particular, I recall going so far as to read vendor-specific documentation for someone, and providing example code to parse the binary data in question. It was probably an hour of my work and I didn't even get a 'thank you', much less any reputation bump.
Talk about devaluing yourself and your industry...
(incidentally, I don't know exactly how much rep I have, since the myopenid login I was using just stopped working one day. No idea why, and there doesn't seem to be a mechanism for fixing it. Edit: I managed to log in again. It appears that if you log in to MyOpenID.com for account management, any subsequent attempt to log in to SO will attempt to use that account's credentials rather than the intended user account credentials, and the error results are absolutely useless)