IMHO, Irina Slutskaya will win the Olympic gold medal if she stays on her feet and presents two clean programs. She seems to be the judge's favorite, and as a European who will be competing in an Olympics held in Europe, she will have a sort of home-court advantage. Her artistry leaves something to be desired, but she's one fierce, determined competitor, and she unleashes triples with a lot of speed, power, and confidence. As the defending World Champion, she is the favorite, as far as I'm concerned.
Remember that Irina nearly won the gold medal in Salt Lake City. Two of the judges awarded her 5.9 for technical merit, which was way too high (IMHO), as she made several errors in her long program. However, those judges were from Europe, and they love Irina. Things may be different now, but I believe the judges will bend over backwards to give her the gold medal. This will be her third Olympics, and, well, at the age of 27, it may well be her last.