Yeah...it's a real bitch about all the negative SJ stereotypes. But I can kind of see why there aren't a plethora of them on here.
One of my roommates (and best friend) is an ISFJ. I introduced her to MBTI, she took the test, read a little bit about her type, said "oh hey, that sounds like me" and that was that.
She told me she just doesn't particularly see the point in MBTI (or talking with strangers online about it). She's all about "real-life" interaction with people she knows or has known or could potentially get to know and spend quality time with. She thinks my whole forum thing is a little odd (and super nerdy), which I find funny because I don't really share her interests at all, either (knitting, cheesy movies/TV shows, cooking, church).
But I really like asking her questions that are brought up on the forum and discussing them with her. So she knows what kinds of discussions go on here and she finds those discussions very interesting, but it's just I think that she'd rather talk about it in person with her close friends and relations. She's a very private person and I can see how she'd think that forum posting is too impersonal and non-private.