Its not like his "money where his mouth is" approach worked. Look at the companies he invested in...they are very mediocre. A few social sites(one for dogs/one for dancing), a video site(seesmic), and an internet storage site. Nothing truly spectacular or ground breaking. Nothing that had any major success. I don't think he is yet to have an exit....I don't count edgio because that was a joke exit.
The only thing in his portfolio that was successful is Techcrunch
If that is true, that might be why he is divesting. I really don't think his investments are unethical, as long as they are always disclosed.
But his investments might slightly affect his objectivity, and get his credibility attacked. And since they are not success, there is no reason he should keep them.
frankly I think him having the ability to disclose his investments actually was beneficial for him. He was able to plug his sites a lot more times. i.e. any time he covered a competitor
The only thing in his portfolio that was successful is Techcrunch