I've never had anyone try to scam me on this site, but I suspect they target younger folks, who might be more susceptible to that sort of thing. But as long as you have a dollar, there will be someone tryin' to take it...
As far as the pic thing, we've been down that road before. A pic really tells me nothing about your musical ability, and it might not even be you. Everyone is entitled to their opinion, of course, but I'd much rather hear a clip. Yep, it's true the clip might not be you, but by talking to you I can gauge it better. If your clip sounds good, I'll ask if you can send me a chart or lead sheet; if you do, it's a fair bet you're genuine. Maybe you don't like to bother w/ charts; fair enough, but in talking to you, I can get a feel for that, and maybe ask you music-related questions.
Bottom line--it's always a crapshoot dealing w/ strangers, but there are things you can do to get a feel for whether it's worth your time and effort. At least for me, looking at a pic serves no useful purpose except to maybe determine if you fit a band's image, but that's the last thing I ever think about. Gimme the grungy old goomba who can play over the hottie who can't find E w/ a map. But that's just me.