I am aghast that the elected governor of a state would be so corrupt as to try to sell a seat in the US Senate -- Obama's former seat. One would have hoped that the process of becoming governor would screen out people prone to this kind of corruption.
Corruption is a huge problem worldwide. The US has some but relatively little overall. In many other parts of the world it is common place. If a system allows it to happen, or even worse encourages it, it will happen. Systems (political, financial, legal) must either be transparent or have a good mechanism of checks and balances to prevent or at least minimize corruption. The US has pretty reasonable political, financial, and legal checks and balances. Yet it still is not enough to completely stop corruption as evidenced here.
I'm happy that at least one serious academic, notably Larry Lessig, has decided to study corruption in detail. Although his focus is more on the everday sort of corruption vs the blatant corruption that is evident in the case against Illinois governor Rod R. Blagojevich.
Read more in the 12/10/2008 NY Times article: Illinois Governor Charged in Scheme to Sell Obama’s Seat.