Apparently there has been so much abuse of drops on Twitch that Twitch has finally updated their rules on it. You can read about it HERE from Twitter. 

The lowdown on it is that you must be LIVE if you're doing drop campaigns. You can't just have a picture up, or use a VOD anymore. I admittedly have seen a number of channels taking advantage of this before the rules were more narrowed down today.

So let's say you are like myself and you like running VODs on your Twitch but you don't want to be penalized for still having your drops on. Well, you can turn them off during your VODs and you'll still be in compliance with Twitch's updated ruleset on drops. 

You can find how to do so HERE, along with other FAQ's. To learn how to turn drops off, look for the subheading "As a streamer, how do I turn Drops on / off for particular game sessions?"