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).

Is the eBay website difficult to use?

Sure there's a little bit of a learning curve, but eBay is one of the most documented sites on the internet. Any problem you could ever have has already been encountered and eBay has an entire support team ready to assist you with any other issues you might encounter.

Who invested in Foursquare?

http://foursquare.tumblr.com/pos…
http://foursquare.tumblr.com/pos…

– Union Square Ventures
РO’Reilly AlphaTech Ventures
– Jack Dorsey (Twitter (product) creator)
– Kevin Rose (Digg)
– Joshua Schachter (Delicious)
– Alex Rainert (Dodgeball)
– SV Angels / Ron Conway
– Chad Stoller (friend)
– Sergio Salvatore (friend)

What is the most accurate estimate of web browser market share?

There's no great way to track this — virtually no way to track
installed base, for example. You can only really look at share of page
requests across a basket of sites — that's what NetApplications and
StatCounter do. Those are probably the best we have for most Western
countries. Gemius is best in Eastern Europe. There's one in Japan that I
 forget, and a number of ways to track in China. Bottom line, though, is
 that there's no very accurate way to track these — you can really only
 get an idea of trending.

When did Steve Ballmer join Microsoft's board of directors?

January 13th, 2000, according to: http://www.forbes.com/2000/01/13… – "Ballmer also will join Microsoft's board of directors."

This was also the day he became CEO – see When did Steve Ballmer become CEO of Microsoft?

Further evidence that this was his first time on the board: He wasn't on the board at the end of 1998 (http://www.microsoft.com/msft/re…) or 1999 (http://www.microsoft.com/msft/ar…) but he was there at the end of 2000 (http://www.microsoft.com/msft/ar…).

Who invested in Facebook?

Mark Zuckerberg put in some money early on along with Eduardo. Also in the series A round (led by Peter Thiel) Mark Pincus and Reid Hoffman independently invested some money.

Greylock and Meritech invested in between Accel's investment and the DST investment.

Also Microsoft invested $240 million at $15 billion in October 2007.