It seems contradictory, since startups thrive on making radical departures from the status quo, but I think there's a strong case to be made to build your foundation (the stuff nobody sees, but plugs along silently in the background) on tried and true technologies, as opposed to the hot new thing.

Of course, in 5-10 years, some NoSQL solutions will be the tried and true tech, and we'll be arguing whether DoublePluSQL is really worth all the hype it's been getting.