I have written a blog post on this with detailed explanation of the 'anchoring heuristic'.
http://saperduper.org/post/293243288/wikipedia-donators-anch...
I also posted it on HN http://news.ycombinator.com/item?id=1007587
http://saperduper.org/post/293243288/wikipedia-donators-anch...
I also posted it on HN http://news.ycombinator.com/item?id=1007587