Yesterday's Startup School provided much food for thought, and possibly a few blog posts.

To start, Ben Horowitz, a principal at the VC firm Andreessen Horowitz, says there's only room for one product in any tech category. If you end up as number two, you'll end up going out of business.

I wondered if that was true, and if so -- why is tech so special.

He offered Sybase as an example. He said it was an excellent database, but it was number two and eventually Oracle came to dominate. Does anyone still use Sybase?

But in many consumer categories there are plenty of number two's -- Avis to Hertz. Pepsi to Coke. The Rolling Stones to the Beatles. Ries and Trout in all their books, talk about there being three rungs on the ladder. One and two make most of the money, with one making far more than two. And three hangs on, barely.

Then I thought about it some and realized there are quite a few examples in tech where no single product dominates.

In web browsers there's Chrome, MSIE, Firefox, Opera.

In mobile OSes there's iOS and Android.

In desktop OSes, there's Macintosh, Windows and Linux.

In browser-based email there's Gmail, Hotmail, Yahoo Mail.

Search has Google, Yahoo and Bing.