I frequently manage my history by deleting junk pages. Unfotunately "forget about this site" is right below "delete this page". Today I was horrified that it accidently deleted all my arxiv.org abstracts. I had not bookmarked them for months as I have been too busy. As an academic this was really upsetting. It should ask you if you really want to delete this unless it is something that you specifically want to delete. I try to get rid of the outlook page generated for each email I read for example. Either that or allow a reverse the forget about this site option