Silicon Valley - still "the" place?

I've seen a number of articles recently on Silicon Valley, and whether or not it's still the place for software ventures. In that vein, here's a story on Cisco leaving the valley - spotted via Critical Section:

Will the last person/company to leave Silicon Valley turn out the lights?  Now it is 3Com which is moving; continuing the string of companies which have fallen on hard times after buying the rights to name a stadium. (Candlestick Park it will always be...) The key fact: "[3Com CEO Bruce] Claflin has roots in Massachusetts."

I have been wondering for awhile now when the high costs of California would start overcoming the network effects of all the firms/people there. Is this all anecdotal, or is there something afoot here?