If so, why haven't they? There is a common misperception about how well large companies can respond to threats to their cash cow products (and thus many people opt not to enter markets where they will be competing with those theoretical products from the large company).

That said, I definitely believe the single biggest threat to the growth and success of Xobni is their absolute dependence on Outlook in the current iteration. But, by the time MS releases a tool that does some of what Xobni does, Xobni will (I would hope) have a multi-platform version with a dozen additional features. Xobni obviously doesn't plan to stand still waiting for MS to catch up to them.