It's both. The more consecutive CAPTCHAs you solve in a short period, the more likely Google is to assume you're not a human (or not up to any good), but you d

It's both. The more consecutive CAPTCHAs you solve in a short period, the more likely Google is to assume you're not a human (or not up to any good), but you definitely can get google browsing identity (however they tag you as a combination of IP, browser fingerprint, etc) to the point that they won't every consider enough responses a good indicator. I've done it many times, and yes, it usually is fixed within a few hours or the next day.