Aside from just what a solid company Optimizely is, I think that if you read Dan's blogpost you get a hint at the ultimate direction they may be going.

"We firmly believe that 10 years from now people will look back at today and be shocked at how generic, impersonal, and one-to-many what we call the web is... We are striving to become the layer on top of the web that powers that experience."

I'd guess that Optimizely may be becoming less about page optimisation and more about experience optimisation. Should my navigation and experience at Tesco be the same as that of a mother of four or a student? My recommendations may be personalised but what if the entire experience at the site including the advertising, design and calls-to action could be personalised and optimised for key customer segments.

If you've ever used Test and Target you'll know that it can get pretty complicated but equally that that that sort of segmentation can equally have a huge impact. If Optimizely can pull off a way to easily curate site experiences for different visitor segments and perhaps intertwine those experiences with social then they could have some huge topline impact in those companies.