Incentive Installs

Is it ok to use Incentive Installs on google play. I always thought it is against developer terms & agreements. but my friend says it is ok. what do you suggest ?

I think it’s fine as far as giant companies are doing it without adverse effects

Of course it is ok. Incentive installs is an effective method to get more downloads and get more revenues from your app. I have published a post on Blackhataso, you can find some tips about incentive installs to boost your app ranking.
Wish this can help you a lot!