One of the things I was really proud of in my last rebuild of CoasterBuzz (spring 2012, I think) was the development of a dedicated mobile view. It wasn't just a responsive design, but a slimmed down alternate view of the site. It's very fast and low on bandwidth, and looks decent on a small screen. I'm happy with the performance viewed from my phone.
There is, however, a problem. The traffic using the mobile view now accounts for 30% of all traffic. I was not expecting that. It tells you a lot about how people are using the Web. The problem is that I can't high-five myself on building the mobile views, because it's eating away at ad revenue. While there is an ad on the page, the CPM is just awful. Club members of course don't see ads either way, but they're only 3% of traffic, and they've been awesome and paid $25 up front.
I'm considering a number of options, and what I'm leaning toward is making the mobile view available to club members only. Since they account for a huge portion of the site's revenue, that seems fair to me. The days of banking tons of cash on as revenue alone might be behind us. Looking back at 2005 to 2007, those were damn good years. Phones and tablets have really changed things.