Welcome to the official website of the United States of America... we'd like to thank Joe Schmoe for making some Javascript. Now, moving on to foreign relations...
Usually as a developer, its a common courtesy to credit any piece of code that you re-use that someone else wrote within your code. It is also usually required by the GPL or whatever other license the code/plugin is distributed under.
I couldn't give 2 tickles who coded the actual site, and not asking for a credit on the site UI. I do care about external people getting their credit though within the code, as that is only fair.