It's an opportunity fraught with dangers, one I'd like to not have to worry about. The real benefit would be to not have to spend time on backlink building! It would be a simple method for visitors to go where they please and would force search engines to stop relying on link values as a rating factor. They would have their hands full trying to sign a contract with browser developers in order to be the default providers.
Not sending visitors offsite vs not having to link build, hmmm.
If someone manages to make cell devices and tablets take a user to whatever words they choose to turn into a link themselves it would be a game changer, search engines would need to adapt quickly. I wonder if they are already building towards a solution in case it happens.