incrediBILL - 1:49 am on Oct 26, 2010 (gmt 0)
bonus traffic from SE images search
Not to distract from the convo, but I've had my fair share of "bonus traffic" thanks to image leeches that scrape the search image results and then hot link the source.
I had to opt out of all image crawlers and image searches, not to mention implement hot link blocking, just to stop wild and crazy amounts of bandwidth leeching.
I agree that it's best to have anchor text links plus alt text links, and google will give you credit for both regardless of whether or not you allow them to put you into the image search scraper cesspool.