Edit: So many people are misunderstanding the word, 'favorite' here. What I meant here is oddmaker's favorite. Suppose, a competition is held between two teams 'A' and 'B' with odds 1.2 for former and 2.0 for latter, then former is favorite, and bettor can bet on this favorite without having iota of knowledge about sports itself and still likely win the bet.
Betting on the basis of the odds does not guarantee anything. Big odd can still be humiliated by a team with small odd, I have seen it happen in different occasions so I don't rely on odds only when making my selection, so if choosing a favourite is based on the odd, I don't always go with the favourite but what will give me the best result I want.
Sometimes I even avoid certain matches before of the small odds given to them which I consider not worth the risk.