While ya'll are talking about multiple romances, I'll just put this here:
I actually had a very strange thing happen in current play through in Act 2. I romanced Anders (no that's not it), had given him his amulet, done dissent, questioning beliefs, gotten my kiss, and my visit, and he was "moving in". The strange thing was, after I finished A Bitter Pill the heart option for "Don't Go" was there... I didn't take it, I was worried it would mess Anders up some how. Thing is, I only flirted with Fenris once, in Act 1 during the after recruitment quest talk. Shouldn't the heart have not been there at all because of that, as well? Then Isabel showed up at my house with a heart option, and I hadn't flirted with her at all... and there was one available for Merril's Questioning Beliefs, and Sebastion kept having them. Like I said, I didn't try these, because I didn't want to mess up Anders' Romance.

I thought the hearts weren't available if you had Anders already romanced? Or do they just give a different reaction? I don't remember seeing them on previous playthoughs. Perhaps it has something to do with the patch, or installing Sebastion after the patch rather than before... or maybe I just found the magic "whoopsie" button by accident?
Apparently it was the "let's all try to romance Hawke at once" playthrough...

Huh, that was ramble-y. Oh well... Anders!