Is BMW going to buy sponsored GIFs? Is McDonald's? Are major CPG companies going to buy sponsored GIFs? I think TV shows and major studios have a good use case for this, but even if the sales are constrained to suitable markets, and healthy, will those sales support a $600mm valuation, or even keep the lights on?
Ad sales work well when you control a platform with a lot of eyeball-share, and when you have strong profiling. I don't think Giphy will have much of either, and if they do, I think the they won't have all of those attributes available (i.e., giphy.com is hard to build facebook-level profiling on, but is easy to control ad units on, GIF keyboards/facebook/various integrations are high-eyeball, but someone else controls the profiling and you can't control the ad units etc).