Will all of these new office developments lead to new tenants, though, or will it just be more vacant office space?

Other than the Google building mentioned in the article and the possibility of Nokia expanding into the 331 Fairchild building, I don't hear any other names associated with these new developments.

What are the vacancy rates of commercial real estate in MV currently?

Office vacancy in Mtn View is a bit below 10%-- down from a year ago, up a bit from the beginning of '08. This is better than the Peninsula at large, also better than Silicon Valley overall. The market is slowing down, however.

Really, though, that isnt all that relevant. None of these new buildings will be ready for occupancy for a good year or more. Impossible to say what market conditions will be at that point, but its likely that the developers taking a risk now in a weaker market are making a decent bet on the future.

A lot of the vacant office and industrial buildings in Mountain View are of the smaller, single-story variety left over from the 1960's and 70's - too small, inefficient, unusable, poorly designed and constructed, insufficiently wired, insulated, lit, etc. I think a lot of these are the ones that remain vacant nowadays because they are now considered obsolete in this day of the sleek, iconic, "Class A" corporate headquarters.

With this new building boom, maybe Mountain View can get something that they need a good Hotel