The ad units are clearly marked as ads, and they’re a different color than your regular email messages. But because of the differences between Gmail’s mobile and desktop interface, it’s a little harder to ignore ads on a mobile device — but the good news is that they should only show up in Gmail’s Promotions folder.
They won’t just clog up your inbox.
There’s not a lot of real estate on a mobile display, and an ad that takes up the spot where you’d normally see your first message is kind of hard to ignore — which is good news for advertisers (and probably for Google), but not necessarily for users. And since these ads are limited to the Promotions folder, odds are they’ll show up along with promotions for things you actually chose to look at.
On the other hand, there’s a chance you might actually get ads, coupons, and other promotions for products you actually care about — after all, if nobody ever clicked on ads there wouldn’t be much reason for companies to continue through dollars into internet advertising.
So if you really like an ad, you can add a star to save a message.
via Android Police