1. Nope, I don't hide. I don't have a 70 to boost yet, so my characters level via questing. And in cities I usually put my slaves on /dance in the AH, just because I think it is silly and cute.

2. I have received no hate whispers yet. Since I only triple box, and my two /follow characters are clones, maybe it isn't as obvious what I'm doing. One time I grouped with a guy who didn't realize there were four people in the group until he noticed the number of character icon pictures! I do get whispers, though. Lots of "u boxin?" and "omg, u mulitbox, can u halp me w/quest, plz plz plz?" I play PVE; I'm sure PVP servers will have a LOT more hostility, but even on PVE you are very visible to the community, which isn't necessarily great if you're a wallflower.

3. Never that I know of, but again, this is probably worse on PVP servers.