I agree. It's interesting because nearly all the GIF searches I use on a regular basis are terrible, yet I wouldn't be too perturbed if I were given relevant/fu

I agree. It's interesting because nearly all the GIF searches I use on a regular basis are terrible, yet I wouldn't be too perturbed if I were given relevant/funny/interesting GIFs that contained product placement (say, a GIF for "cheers!" might be someone raising a glass of Coke). I think the problem might be that advertisers can't control context. Someone might say something vile (but legal) on Twitter and get lots of meme GIFs in the replies that advertisers would be very unhappy about, and it's a more direct connection than having your sponsored tweet appear in the chain.