IMHO the single biggest reason that tech companies haven't resumed hiring is uncertainty. Management teams don't trust the tepid recovery and are reluctant to take the brakes off spending, fearing that they will simply have to make cuts again if the economy once again tanks. Ironically more hiring would likely help the recovery gain steam, but firms don't want to start the hiring until the recovery shows more strength. It's a Catch-22.
Your lead paragraphs in this article are dead on. I've been following the "recovery" efforts of tech companies since early 2009 from a PR- and marketing-spending perspective and I can tell you that most of them are hoarding cash, slashing costs and not hiring quickly enough for key positions. My sense is that they are hedging their bets against the other (economic) shoe falling. As a result, momentum in innovation, product development and their position within the competitive landscape is suffering. With most of the cost-cutting measured fully implemented, it will be interesting to see how they fare as more aggressive competitors enter their market space. Perhaps they'll smarten up and start hiring and paying for engineering talent...but I'm not yet convinced.