Yes, but then there are a lot of startups in the Valley and the vast majority are not Googles or Facebooks. It does tend to look quite bubbly. And from an investor POV perhaps Twitter is not something to aim for, profits-wise.

Another problem is that the current bubble (if you want to call it that) seems heavily driven by the tendency of Google and Facebook to engage in enormous acquisitions of otherwise unremarkable or even no-hope businesses. A lot of companies don't seem to have any business plan beyond "get bought". But the big fish want companies down the road so the employees can all relocate to HQ. They don't typically want to acquire companies in other countries unless that company is truly something unique.

> tens of billions $ ipo level success; see facebook, twitter, google

But those make up a tiny proportion of business.

define success. most VC funds lose money every year.