When should I cut my losses?
In What's the Point, I described the benefits of knowing what you want. But what happens if you meet someone online who seems like a good match but she doesn't seem to know what she wants? She says she'd like to get together but when you try to make specific plans, she dodges them. She responds when you IM her, but she never initiates. She goes hot and cold on thinking about moving the relationship from theoretical to real...
You're dealing with someone who either a) doesn't know what she wants, b) just wants attention or c) doesn't know how to say no.
In the case of her not knowing what she wants, there's certainly a possibility that she'll figure it out, and you may be able to help her along the way by asking questions. I'm sorry to say, however, that lots of people effectively avoid such questions, especially from strangers, by putting on a social script -- things they've heard or thought but that don't actually get to a real answer -- so that technique may or may not get you anywhere.
In the case of someone who just wants attention, there's obviously nothing to be done. I'd like to think that these ones stand out for their narcissism, but I rather doubt that.
And, of course, in the case of someone who doesn't know how to say no... well, this is a huge social problem that lots of women have. It's incredibly stupid, but there may be any number of understandable reasons behind it: she doesn't want to hurt anyone's feelings, or she just never learned the value of "thanks, but no, thanks," or who knows what else? At any rate, there's nothing to be done. Move on.
Unfortunately, there's no good way to sort out which is which, and in any case your best bet is to figure out the limit of your patience and be done with it after that.
