I have only ever been to one so. It was pretty fun actually, not 'grabby' at all as it was a surprise. The only problems I had were with the organisation part, as it was to be a banners/balloons sort of do, some people weren't doing their bit to chip in and that was quite annoying. But maybe they just weren't that into the idea.
The thing is, when you've done one for one of you friends, when other friends get pregnant the 'baby shower organisation' talks begin again. I'm going to another surprise one soon which is for a very anxious lady who has had quite a difficult pregnancy after several m/c. I told one of the main organisers that perhaps we should tell her what we were up to, take the shock factor away. Then she has some control over how the evening goes, or if she wants to bother with it at all. Organiser said no it's ok, have contacted her DP and he says she'd love it. He knows her best I suppose.
I personally wouldn't want one, not because of not wanting to be thought of as grabby, but I reckon at that stage of pregnancy I'd be too knackered and bloated and not want to bother having to entertain anyone. I know what my friends are like though, and they would throw me one anyway, so I wouldn't want to look ungrateful either.
I've seen youtube vids of men at baby showers, it's nice to involve them some way, but at the one I went to, ladies stayed in the house and the men folk went to the pub. Agree with the person who said if baby showers are sexist then surely men's headwetting sessions are too!
Sorry for length, just an intriguing subject!