This is actually why I kinda like the heart icon. I remember talking to Kaidan once in ME1, one single time in an entire play through and I ended up in a romance with him. It was really annoying because I was trying to keep that Shep single to romance Thane in ME2. And I don't like being a jerk to my companions, but ME1 kinda forces you to if you don't want a romance. So yeah I like the heart icon because it helps me avoid unwanted romances. (ME2 was really good at having a middle of the road friendship path though without icons so I don't know.)
What I would like to see is some subtly on the part of the PC when initiating a romance rather than "Oh, you're so handsome/beautiful. Love me!"
I haven't played ME yet (I plan to at some point!) but I don't think that the problem is "ninjamance" here, it's more the fact that if a romance starts, all the others ends. Which completely sucks I agree.
That's why I think Origins got it right, you could initiate romance with all the characters at the same time if you wanted to, and you could also decline politely if they showed interest. I agree with Chari, the first time I played and Alistair started showing interest while my PC was just being a nice friend, it really felt like a surprise (a good one).
I completely agree with having more subtle options, Hawke was sometimes just... no.
Well, maybe getting rid of the heart is not necessary to keep the surprise. If hiding the icons is viable, I guess it could satisfy almost everyone. The problem is those overly simplified paraphrases that forces you to use the icons if you want to have at least a vague idea of what the character is going to say.