You are making assumptions that are unwarranted. There are other uses for MD5 besides data integrity and data security. For instance, I generate an MD5 hash of

You are making assumptions that are unwarranted. There are other uses for MD5 besides data integrity and data security. For instance, I generate an MD5 hash of a user's email address and use that hash for Gravatar. While someone who knows quite a bit about MD5 and the other person's email address, can force a collision ... all that would get him would be the other person's avatar image ... which is public anyway. In other words, using MD5 is perfectly fine in situations where collisions don't pose a serious problem.