If I'm Apple, Google, or Microsoft I'm going to care a lot because - native or web - users need a platform for applications, and those platforms represent a) revenue potential (see the iPad business) and b) a potential control point (see MSFT for the past two decades). As far as I'm concerned, the native vs web application question is secondary to the platform question. We're going to have both, and yes web clients will increase share. That doesn't change the fact that whoever is supplying the most popular platform for apps - web or native - will have control and profit potential in spades.