[willie24]

it's not an advantage. in general, you shouldn't do it.
if you're more comfortable with a double or triple stack, doing it once or twice is fine, but be aware that it comes with a slight EV disadvantage (relative to your first buy-in) every time you do it.

other players doing it doesn't hurt you at all- in fact it helps you (by building the prize pool more than it decreases your fraction of the prize pool).

if you are a certain type of good player, you may gain from immediate rebuys, but you are always better off spending that $ on a buyin to another rebuy tournament than on a rebuy. for example, your EV from a $100 buy-in might be $180. the EV from the first rebuy might be $120. the EV from the second rebuy might be $100. and from the third, $90, from the fourth $85, etc. That's just an example, and it might be any secquence of decreasing numbers, but the point is, they are always decreasing. the point at which they become unprofitable may vary, but every rebuy is always less profitable than the buy-in.

note: this assumes that rebuys get rake-taxed at the same rate as buy-ins. if they don't, that is a slight boost in EV for rebuys.