Another commenter pointed out that Giphy is integrated into many products and buying Giphy is a way to get metrics about those products.

Makes more sense. But it is easy to replace it with another giphy. Especially when there is privacy reason.

Question os: How many will switch it out? Giphy has a big collection of images and works ... swapping is effort and brings different (unexpected?) results.

Create a proxy that exfiltrates their active database while providing anonymity.

Again, a small number of people might do that, if one gets too large by chance Giphy/Facebook will attempt to block them. Most users and integrations will be kept. As people stay on WhatsApp etc.

For $400m?

Eyeballs. It's used casually by many millions of people daily. That's all that's needed to justify price.

I'm guessing Data. Trends, among others.

Makes me wonder whether you could use trends in use by employees at a large company to do some trading. If their gifs turn negative in advance of an earnings report, that’s probably not a good sign.