in my opinion, just because things like adblockers will come out doesn't mean the majority of people will use them. think of spam: why does it still exist? it's because of that 0.1% of people that view them. say 2 million people receive a piece of spam (a very low number by today's standards I'll bet) and only 0.1% view and respond to it by purchasing the service or product. that's 2000 people who bought your product. if you spent even $1000 on your spam services then you've still earned $1000. For a small business that's nice piece of cash for very little work. so they continue to send spam.

Anyway, my point is that the same thing works with something like ads on a cell phone. Sure, through viral discussion a large number of people will block their ads, but that large number will probably be quite small compared to the total number of people who opt for a FREE(!) cell phone. so google will continue to use ads to cover costs and make money - as long as the percentage of people watching and responding to ads stays high enough... but that's another story :)