Mobile Apps a bubble?

I've been thinking about the mobile app market and have begun to think of it as a bubble of sorts.

This is given the case of Umano, an app that produces no original content, has no community and pays voice actors to record news articles. It has 40,000-60,000 daily users (I've created websites that had more - when I was 14) & I've seen people valuing it as high as $100M. This is a ludacris valuation.

I'd compare this relative to Yahoo about to acquire Tumblr for $1B. Tumblr is the 3rd largest social network with a large portion of it's user-base certifiably addicted to the network, it has had problems creating revenue but being one of the 40 largest websites in the world is sure of a much better launching point than a app with no unique quality.

Tumblr for $1B is a very ridiculous undervaluation when you consider Waze & Instragram both about to be (or already have been) sold to Facebook for the same figure, $1B. Instagram has proven to be a success for Facebook as it has a tremendous user-base but it has produced very marginal revenue for the company if any while Waze is a social GPS app. Waze has far more potential to produce longterm revenue than Instagram but it does not have a hundredth of the user-base that Tumblr has so how in the heck is it being valued the same?