Mobile Internet Users do not click on ads  

I think that adding a voice calling application to Twitter is a ridiculous idea, especially if the conversations can only be two minutes long. From my viewpoint most of the people that I know on any social network are friends, most of which I already have phone numbers for. So if I really wanted to talk to them I would simply call them, rather than going through Twitter first. Second if I really wanted to have a conversation with anyone about anything remotely important I think it is safe to assume that the conversation would last more than two minutes, therefore making the cut-off extremely annoying to me.
On the other hand if you are following someone you don't know and for some reason you must speak to them without tweeting, this would be a good alternative.
I guess all in all I think this is kind of a creepy thing to do even if you can choose to keep your number private and ignore calls.

I can see why no one wants to click on ads. Who does? I have an iTouch and use it all the time on campus for email, checking websites, etc... I think the reason there are less ad clicks on mobile devices is because when people are using them, they are usually on the run, or are multi-tasking. Also it seems to take a little longer to access sites on mobile devices. So why click on an ad that would prolong you even more from getting to your destination?