There are a lot of companies accepting bitcoins in pretty nice volumes.
Are they transferring out to fiat as soon as they make a sale?
Are they waiting until a certain day of the month and dumping coins?
Since Dell can't pay its employees in Bitcoin or buy its advertising in Bitcoin, there is a need to get back into dollars.
But, until advertising agencies and employees accept it, the massive flow OUT of bitcoins is going to be pretty rough.
However, you have to remember that companies like Dell don't rely exclusively on Bitcoin, so they don't need to convert all of the Bitcoin to fiat - their fiat payments more than cover the costs of doing business. That being said, I can't say if most of the companies accepting Bitcoins actually keep them or not.
However, I have been seeing a rather positive sentiment regarding company adoption of Bitcoin - which if anything should be leading to an increase in price (which is exactly the opposite of the case. I'm not sure whether the market is adequately handling the exchange of coins in the same volumes as being accepted as payment by companies but thus far it hasn't really made a big overall impact, unless you assume that the recent $100 USD fall is a result of that.