That's what the word "bubble" refers to, though. If the OP didn't mean a stock market bubble, he should explain what he does mean. A "bubble" of investing? Why would it warrant the analogy of a bubble? What horrible things happen if and when VC investments don't pan out?
What people are trying to call a bubble is actually just an increase in investment by VCs, sometimes good investments, sometimes bad, and sometimes there are overvaluations.
But if you think we're in a bubble, you either don't remember the real bubble of 1999 or you misunderstood what the problem was.
I suggest you to check few graphs on Google/Yahoo Finance
Considering the deep trough we just came out of, it makes sense that we see a stock market uptick. Moving up != inherently bad.