If you are new to betting, the answer to this question may seem fairly obvious to you, and your answer would be no. But for people like myself who have worked in this industry for years, you would be surprised to know that it is actually an effective strategy if you know what you are doing.
The good thing about betting on underdogs is that they always have the ability to pull off a shock upset and in return, you get very good odds for it. If you do your homework and study the statistics and form a little of these underdogs and also the form of the opponent, you might find something in them that actually shouts out at you that maybe they are not such underdogs after all but perhaps the Bookmaker has not looked at recent form in too much detail or it could be the fact that everyone will back the team they are playing if a very big name, some just because they are a very big name and there is no way in which they could lose the match right? For these reasons you could be getting much better value supporting the underdog.
Maybe the other team has some star players missing through injury, International duty, illness or suspension or maybe them and other players are not match fit, maybe it is a cup match and they have decided to field a weaker more youthful side. All these are things in which to consider when placing your bet on an underdog, if you have a little bit of time to research you could find enough reasons to convince yourselves that actually the odds for this underdog on this occasion are actually good value for money and worth a bet.
The opposition could come into the game with overconfidence and not take the underdog seriously enough or maybe they are not overly concerned about getting a result in this match because they have a big match coming up a few days after this one and so are resting players, trialing new formations etc.
Betting on a underdog and then giving them all your support throughout the match can be a very thrilling experience and if the bet comes in, you can expect a great return as well. They are fun bets to take and due to the odds being higher than the standard bet, you don't have to risk as much to potentially make a lot of money from it. Watch for line moves / odds changes that indicate that a significant amount of money has been bet on the underdog. A good time to bet on football underdogs is later in the week as odds of favorites tend to rise through the week.
Bookmakers have to take into account public opinion when setting prices otherwise they will have a lopsided book. This public opinion may well not be your opinion, and if you have studied the game or just feel that the underdog is overpriced then you should bet it.