Normal to bewcome good friends with people you once disliked?

Real life or web.
I know ion the past, there have been people I thought I hated when I first met but got to talking to them and somehow, a friendship evolved. Not like a deep relationship but it just gets to where I cannot even remember why I didn't like them before.

On one forum that I lurk, someone came along and she was my least favorite member. We got into it a few times (cause fighting on the web is like competing in the special Olympics) but at some point, we got to talking. It was when I posted something that the rest of the forum gave me shit, thinking I had betrayed them, yet she jumped to my defense.

Of course the opposite situation can suck when someone you thought was cool at the start later turns out to be a prick. It is like often when the shit hits the fan you really find out who is cool or not.

So, does it seem normal that some of our friends are often the ones we thought were bitches/pricks at first?