User-accounts mean limits can be applied per-user instead of per-IP. Especially when a lot of us are connecting from the same office/site, or the same corporat

User-accounts mean limits can be applied per-user instead of per-IP. Especially when a lot of us are connecting from the same office/site, or the same corporate VPN. But being logged out is more efficient for cached responses. The more load the site is under, the more this pays off. It makes sense that they're both true - it's not a case of which is more recent, it's what problem they're solving.