Shopping – it can be dangerous if done the wrong way. Obviously, you have to be careful and take the right precautions.
I am referring to a case in which you approach it the way you approach any shidduch – by using a shadchan and references, and trying to figure out who you know in common, and checking out the person carefully. If you do it that way, it is no different than Saw You At Sinai and Frumster which are both recommended by Rabbanim.
Also, I was referring to older singles. I would not recommend that “younger singles” meet that way. Dating when you are older is completely different than when you are younger.