Google's department in charge of making a hash of trying to separate content spam sites from others is warning website publishers of a new algorithm dubbed Penguin 2.0 to come this summer that should shake things up a bit. In particular, "native ads" seems to be in its sights, with two criteria listed as necessary to not suffer the wrath of the new formula.
1- Any paid placements on a site need "clear and conspicuous disclosure," or poof, you're in Google jail; and
2- If you sell placements that have the effect of raising advertisers' rankings, then, pow, you'll be subject to some equally mysterious Google penalty, which may or may not be acknowledged by the firm, and which may or may not be reasonably redressed in some predictable fashion.
That second policy is notable in that it creates a bit of a liability associated with an effect on an advertiser, rather than with a specific behavior on the publisher's site. Since many have experienced significant organic search bumps after starting Google Adwords campaigns, it will be interesting to see if this Google effort will be designed in a way to exempt Google's own potential transgressions.
New Google Algo Imminent, 'Native Ads' in Sights - MarketingVOX

There you go, the killing machine ready to wipe out sites that display ads aka killing competitors ads publishers.