His background contributes to his mercenary attitude. I used to hate him for it but to be fair almost every time he's moved the selling club has been happy to see the deal go through.
The last two clubs that sold him won the CL the following year...
Inter used the money to get on top of Eto'o; Sneijder, Milito, Motta, Pandev, Lucio etc. All starting players in their CL run.