Countering Payment Reversal Risk for Merchants: How long before online downloadable digital content / services merchants will proclaim that they only take Bitcoin due to the reversability of other payment methods, and the irreversable nature of Bitcoin payments?
Countering Bitcoin price fluctuation Risk for Merchants: The merchant of the downloadable content / service can also protect themselves against fluctuating bitcoin prices by exchanging the received bitcoins immediately (programmatically) after receival.
Countering Bitcoin liquidity Risk for Merchants: Pricing of goods/services can take cognisance of the depth of market liquidity on major exchanges. If your product is worth $50 dollars for example - and 100 customers are expected to order it per hour - it gives you $5000 - if the depth at MtGox of bitcoins wanted is $5000 at an average price of US$16.45 for example - you can convert your US$ into bitcoin (programmatically) by this conversion rate. So depending on your product price and product volume you can offer a bitcoin rate on the fly if your site is linked to Bitcoin exchange data.
Simple Merchant shopping cart bitcoin transfer button script (should just be able to replace paypal/credit card payment link in shopping cart software with bitcoin enabled transfer link): https://en.bitcoin.it/wiki/BitWillet