Most people are overreacting. Kidnapping was very serious in the 80's and 90's. There were several years in which there were more than 3000 kidnapped persons. But right now this is not the case. For example, between january and july 2010,
only 3 foreign persons were kidnapped in Colombia. In that same period, more than 700.000 foreing persons visited Colombia (
I assume that because between january and june there were 678.177). That is, the odds are less than 0,0005%). 2 of the 3 kidnapped persons were released in the next few days by the police. The other one was a millionary japanese guy, who was kept for almost 5 months by common criminals who later delivered him to the FARC and it was probably paid a huge ransom for him to be released. I don't have more recent data, but I don't think things have worsened, considered that the kidnapping values have been decreasing.
I have myself voyaged around the country with quite a few european friends, even to regions considered somewhat dangerous, and nothing happened. Not to suggest you to go to the worst areas in the country, but it is pretty much safe. Actually, the drivers are quite more dangerous. They can be real jerks. One of them ran over Soler last year (or 2009, I don't remember), in what could be considered the only accident in which Soler was involved but wasn't caused by him.