Yeah, that assertion is baffling. Flickr is a photo service, it absolutely could've worked well on mobile...one of the first paid apps I ever bought was a third-party app that made it easier to use Flickr. Flickr famously was caught unawares by the trend set by Instagram and, well, Hipstamatic. In the news business, Yahoo News is very well known. Again, nothing inherently un-mobile about that product.

Perhaps few of Yahoo products seem addictive enough to be mobile breakthroughs, but that seems like a chicken and the egg thing. I liked using Twitter a lot from the desktop, but having it accessible via phone made it even more addicting.