Same here. I usually add them as a fan if I look at their profile and can't tell where they found me.

And then remove/block them later if they never update/look like spammers.

I've been blocking 'em all - I don't quite get the "Fan" thing, myself.

Well Fan is like if someone wants to read your stream but you don't want to read theirs.

More accurately, it's that someone wants to read my plurks, but doesn't want me to read theirs. No thanks.