1. The claim was that in crappier weather people tend to stay in and work instead of lounging about in the sun. That's not to say that this is true, but simply stating that SV has good weather is missing the point.
2. Just because there are lots of people in the Valley to recruit doesn't mean they are automatically better than workers from elsewhere. The ease at which you can fill your company with seemingly qualified people is not tied with how good of a product of how successful a company will be. The article makes a good point about ship jumping and spiking salaries.
3. Your again confusing quantity with quality. You'll still be groveling to get a chance to present at any of the top level VC's in SV and since there are a lot more presentations being made, the chances that they've seen same idea you're trying to present three times already that week means you'll still likely have to settle with the bottom of the VC pile. That is unless you have a good idea and a good presentation in which case top VC's in Boston, Tel Aviv or any other place would be just as happy to have you. This is all besides the fact that plenty of successful startups bootstrapped themselves to success.
4. A startup does not need to 'Exit' in order to be successful. Not all startups have the goal of hoping that Google/MS/Yahoo/Ebay will one day look down pick them as the prettiest girl at the dance, some startups want to be the ones doing the picking and plenty are fine just making decent money doing something they love. A narrow focus of an Exit only strategy puts many startups in an early grave despite good chances of becoming successful in other ways.
5. Good board members can be found just about anywhere on the planet and with teleconferencing technology as it is now, being located in the same city as every board member is not necessary and actually might be a hindrance. Besides that, I'm not quite sure what three other bubbles happened in SV other than the Dot Com one?
There are plenty of good reasons to startup in SV, but that don't make it the only place where a startup can be successful.