LinkedIn is doing some really great stuff. IMHO, they are the company who has done the most interesting things with OSS search technology and given back to the community.
I'm obviously a big fan of LinkedIn, and I see them as a poster child for faceted search. I hope they take the next step and do interesting things with the skills data that is latent in their profiles. But I'm happy that they took the bold step of putting faceted search front and center--and that they're seeing great returns on that investment.