Facebook has been trading for a while on secondmarket (a secondary market for 'qualified' investors). The prices have been pretty stable there. These people evaluate the markets in much the same way that every other trader does, and so their value calculation is going to be in line with what any 'real' trader might come up with.
Retail investors, the folks who made the dot com bubble so spectacular, have largely left the market as a mover. So any 'creative' valuations are probably not going to drive a lot of trades.
So trading on the NASDAQ opens up the process to retail investors but they aren't a significant factor, that leaves the more experienced investors and they have already valued the company and shown that on second market, so that the stock moves at all is probably more along the lines of the daily/monthly variations you might see in a Google or Apple or Groupon, rather than the sudden IPO pop of people who wanted to own the stock but were unable to get their hands on it.
That makes it a 'good' sign in the sense that the folks who valued the company in the secondary market were making pretty good guesses on the value. It is also another 'non-bubble' sign in the sense of over-exuberant participation by the retail investors.
Edit: replace 'going going' with 'not going'