No. Theft would mean they no longer have the service once I've taken it.

Me taking a copy of Shrek 2 at the local store and not paying for it is theft: the store can no longer benefit from Shrek 2.

Google can re-send the exact same bytes to someone else. All I've costed them is what it costs to send those bytes over. But then, would you consider going into a store, loitering for two hours, taking the sellers attention (therefore, costing them time that they cannot use to sell things to other customers) then leaving without buying anything theft ? Most reasonable people would say no. We'd all agree it's a dick move, but since corporations are not people, it doesn't matter.