FWIW, if you live in San Francisco it is common for your ride to be $10-12. With the recent Uber Pool promos it was $5 (or now $7). So at least in one market, there are many cheap rides being taken.

That said, in-app advertising is not the kind of premium/magical experience that has so far defined the Uber brand. That clash of clans banner looks downright painful. I don't expect ads any time soon; it's more the kind of move I'd expect once they're done being a growth business and shift gears into cash extraction. Years off at the soonest.

Personally, I've taken rides for $45 split 4 ways, but more often than not it's $5-7/per trip for two. I'm no power user, but also probably wouldn't call a cab in those situations either.