Since someone within TC stands to profit from the company they are writing about, isn't a disclosure a good idea? I agree that it's not entirely clear-cut what to do here, but IMO to build any sort of journalistic integrity a media outlet should err on the side of disclosure.
Micheal Arrington is an LP in a16z, Benchmark, Lerer Ventures, SV Angel as well as being a General Partner at Crunchfund[1]. I think the disclosure of Crunchfund is enough otherwise, on every post there will be a disclosure stating Michael Arrington has directly/indirectly invested in a startup they are covering with/without his own knowledge. Don't forget this is the same, Michael Arrington who stopped investing when he founded TechCrunch and the ones he had invested in - there was a clear disclosure and he never personally covered them.