One can accuse me of naivete, but I'm not stupid. In my experience, these are people trying to scam me, sell me something, or both.
Here's how you can tell:
1. The picture is of a pretty girl that is way out of your league.
2. The initial message is something small and simple ("Hello" works) as if to judge if the account is active (or the account holder is stupid) without wasting a lot of time on it.
3. The person is not following anyone (or maybe just a handful of people, a lot of whom look like marks).
4. No one is following the person (again, except marks).
I've lived long enough to be wary of overly-friendly sexy women: they usually want something from me, and once they get it, they forget they even know me. I've also been around the internet for a long time: Sexy lipstick lesbians generally don't hang out in gaming boards and once the truth is revealed, they're usually an overweight 40-year-old man living in his mother's basement.