I think one of the major reasons a lot of tech startups are failing is because so many of them don't even begin to focus on monetization and are still stuck on being acquired with a big exit. Even with the whole Lean Startup movement, I think so many startups are still far from thinking the way they need to to make a profit in a reasonable amount of time.

MVPs and customer interviews and everything else are great, but at the end of the day, what's most important is that you target a market large enough to sell to enough customers to make for a sustainable business model. Even a perfect product can fail if a market is too small or worse, completely non-existent.