If they haven't at least emailed or PM'd you to say hello then it's definitely a bit forward. Personally I'd always ask, or let somebody know my details and let them add me if they want to.
Not having your MSN address publically accessable would be the easy way to avoid people like that, so taking it off was definitely a good move.
Ok, just to put things into perspective, the ratio of single bi fems to couples looking for them is about the same as single fems to single blokes i.e. greatly in their favour, so they can afford to be choosy.
I've not seen your ad but you will need to put some effort into making it stand out. If you use the photo ads then you'll probably need to be proactive about replying to anyone you think might be compatible rather than waiting for them to come to you.
The most reliable way to meet people on here would be to become known on the forums or in the chatroom well enough to go to a munch or other social.
It is a silly question.
Those that want to tell you will, those that don't won't, and it'll only be a matter of time before the whole 'cheating blokes' schism rears it's ugly head once more.
Personally my marital status should be obvious from my sig, if you're really that bothered.