Could WebMD be successfully sued if someone gets bad advice from it?

Probably not. WebMD has all of the appropriate disclaimers and doesn’t tell people what they should or should not do. It just is providing general information to educate people.

In the consumer Internet space, how many excellent engineers come out of both college and graduate school each year?

Hardly any excellent engineers graduate every year. Most are going to require time and experience to become excellent. There are a lot of talented engineers graduating, but hiring straight out of school is usually an investment, not an acquisition.

What are the most successful iPhone companies to date?

Apple 😉
(probably very true if you add up all their apps)

then it depends if you question is about:
– actual accumulated revenue on that activity
– recurring revenue on that activity
– number of downloads (free apps -> that would be facebook)
– actual usage

What is the most important space on the Internet right now?

Social Information Organization and Routing – Quora, Fluther, StackOverflow (StackExchange)

Mobile/Location – FourSquare, GoWalla, Bump, Twitter (GeoAPI), Facebook Mobile – Bunch of good data here:  http://www.scribd.com/doc/241293…

Internet Enabled devices – Picwing, Sifteo

Social Commerce – Blippy, Square, Swipely, WePay

What websites retain users for the most number of years?

I used to follow this closely in the paid subscription services business: Ancestry.com was about 20+ months per average paying user; dating sites like Match.com were approx. 6 months.  Those were the two extremes for paid subscription services, I think (though I haven't done a thorough review for a few years).