I'm not influenced by them. If they're trying to sell something I'm not interested in, which are most things, no amount of good advertising will make me buy it or want it. There was one commercial some years ago with a turtle that seemed to be flirting with a cell phone. I loved watching the turtle, but it didn't make me want the cell phone.
When I see something advertised that I'm interested in (like a new pizza flavor or a specific DVD), I'm not more interested or excited about if I see the commercial first. In most cases I have seen the product in the store before I saw the commercial, and I was equally interested in the product in either case.
Attractive people in commercials make absolutely no difference to me. I don't even think most of them are that good looking. I found the guy in the Levis commercials from 1993 (the Ring of Fire) really attractive, but it didn't make me buy or want Levis jeans. It just made me enjoy the commercial with that guy.
A couple of years before it was aired here, I got a couple of Levis jeans though, for the very simple reason that it was the in thing among some people in my junior high at the time. Like most at that age, I could be influenced by my peers. At the same time I also bought a Levis jumper because I really liked how it looked, I wasn't even consciously aware it was Levis at the time; I just dug the thin grey arms and the thicker body part in blue and the white text on the chest.
Commercials that try to play on demographics I should relate to make me nauseous. For instance, so-called female things will come with children that I'm supposed to find cute (but I don't), or they play on sex (which makes me uncomfortable). My reaction to them is the same as with manipulative human interest stories in the news, I'm repulsed by them.