However, 300k requests per day surely is enough that this could be considered a sort of denial of service attack and violate fair use.
If Google wanted to, they would scale down their servers for a day, wait for this traffic peak to hit, document how it made the service unavailable to others, and now you have a valid offense to sue for.
illegal means violate criminal code.
> now you have a valid offense to sue for
That's civil, not criminal.
It's pedantic, but words matter.
https://www.eff.org/deeplinks/2019/09/victory-ruling-hiq-v-l...
Yes. That's also what I said above when I said "Google can sue them". It's not illegal is my entire point. You can sue anyone, for any reason, at any time, and even win. That doesn't make something illegal.
If Google sends them a C&D, and expressly forbids them from doing this activity, and implements technical measures to prevent them from doing so, and they continue doing so then they may start approaching the area of illegal (Craigslist v. 3Taps would agree, hiQ v. LinkedIn would disagree).
300k requests / day is a little over 3 per second. That's not much.