The current obstacle I see standing in the way of most merchants adopting bitcoin is that bitcoin has no reputation among consumers, so merchants would be afraid that putting a bitcoin payment option on their checkout page could reduce the credibility of their site.

New merchants could benefit from adopting bitcoin as the growing bitcoin community, looking for places to spend their currency, provides traffic to their site, but a good portion of established merchants would not want to jeopardize their existing revenue-streams in any way.

One possible bridge to mass adoption I thought could work is offering established merchants a 'bitcoin only' page that the rest of their website is not linked to. That way, they can advertise that page in bitcoin directories, but not risk reducing the credibility of their main storefront by displaying the mostly unknown currency as a payment option.

A possible business model could be a company offering to create this 'bitcoin page' for merchants, in exchange for a percentage of revenues produced through that page, and the company advertising that page on behalf of that merchant.

This might allow the number of merchants that accept bitcoin to increase to thousands, or even tens of thousands.