Why would anyone think it's a bad thing? Widespread merchant adoption ix exactly what every wants and needs for bitcoin to become valuable as both an asset and a currency.
A distinction should be made between merchants that accept Bitcoin directly and keep some or all of their bitcoins without cashing them out and merchants that accept Bitcoin via a third-party payment processor such as BitPay which sells the bitcoins and gives the merchant USD. The former is much rarer and not at all easy to do since the Bitcoin economy is still quite young and undeveloped and the BTC price is still prone to wild swings. The only large, mainstream company that I know of that keeps a portion of their BTC in the form of coins rather than instantly cashing them out is Overstock and even then, it's only a small percentage. Most of it still gets converted to fiat.
The problem with using a payment processor such as BitPay is that selling the coins and exchanging them for fiat creates a downward pressure on BTC's price resulting in lower bitcoin prices. Not a big concern for companies like Dell since they automatically get paid in fiat and never even see the bitcoins (it's the payment processor that handles that) but for us Bitcoiners, it's not 100% ideal.
As for me, I'm on the fence as to whether or not such things are positive or not. Some people like cyberpinoy see it as a terrible thing. The majority here seems to view it as a positive thing although most people generally agree that it creates a downwards pressure on BTC price.