Why would anyone be willing to do captchas? It is just a waste of time for regular users.
I also had a similar experience when I searched for many different queries in such a short time, I got hit by captchas for a while.
What other ways would you recommend them to use to distinguish your “many different queries in a short time” from automated bot attacks, etc.?
I am not a DoS/spam expert but first things come to mind are :
- Google account credibility (I have a very old Google account and this should provide me some trust from Google's perspective)
- Malicious word analysis in search queries
- Browser/device information to determine authenticity of the search (if I am at home or connecting over a Tor network)
- Gradually increase the response time for the queries
On top of those, Google is a machine learning company and I am sure this process should be automated by now without requiring filling of any active captchas.