>My bid kicked in again to $2.74? then someone came in and knocked me off at $4.51.

No, your proxy was $3.50 so they knowcked you off by one bid increment (which I think is $.25 at that point) so they were at $3.75.

>this time it was just to make sure that someone didn't outbid me again

But you understood that you may have already been outbid, if the high bidder had bid $7.00 (as opposed to $4.51) he would have ended up outbidding you.

>I also think that I probably saved another person some money by not giving them the opportunity to bid again

Why? Perhaps the other bidders had already bid theost they would pay.