Steve Bennett wrote: ...
And why do you care anyway? Vanity? Curiosity? Is it that important? Is a little piece of text on some idiot's webpage the difference between you contributing your time next time and not? Is the gratification of your name in cyberspace your primary motivation for producing useful free images?
(These questions are rhetorical and deliberately inflammatory. Take the bait with caution.)
A less ego bound reason* for wanting to see some acknowledgment - especially through a link to Wikipedia or the like - is that it is advocacy for the intellectual commons. This could encourage others to get involved or to consider making their content free.
Also if the importance of free content isn't widely understood it will be harder for policy makers to come to good decisions about laws or other public support that might impact it.
Siobhan
*Not that I think there's anything wrong with wanting to see your name in lights - vanity can be a big motivator.