How do you know whether it's common or not? I've sat there several times trying to remember my password, remember whether I used Clickpass or not, etc. Finally, I just decide it's not worth commenting, and close the browser tab. (Posting under newly created account because I still can't figure out my old account's password.)
Password retrieval has been a standard feature for any website for many years. It's easy to do for users who have an email in their profile, and it gives the rest a good reason to enter it. When I created my account I added my email because I assumed that the feature existed. Good thing I haven't forgotten my password.
someone doing a few failed logins before successfully logging in won't look all that different than someone doing a few failed logins and then giving up, which is what most humans would do (as opposed to scripts).
people naturally tend to have a small number of cross products of usernames and passwords...once it gets too large we start forgetting parts of it.
a couple times in the past year i've forgotten my password for hn. after the first time it happened i wrote it down so i wouldn't lose my precious karma.
