I think the president of Colombia is not an unreasonable choice. The selection criterion set out by Nobel in his will for the Peace Prize is "done the most or the best work for fraternity between nations, for the abolition or reduction of standing armies and for the holding and promotion of peace congresses". He has in fact been doing work in those directions, and it has in fact been good work. It hasn't been completely successful, but it also hasn't entirely failed yet (e.g. FARC is not back to open fighting, now is it?) and I think there is a very good chance that it will in fact succeed. We can start arguing about whether it was "the most" or "the best", but I think it's hard to argue that it wasn't substantive work aimed at the things Nobel's criteria indicate.

The Obama thing I agree was rather ridiculous, as were various other Peace Prize awards.