It's easier to throttle people if you have to use an account to access the information.
That's not true in the slightest. I can create as many accounts as I can have email addresses, and I can have as many email addresses as I want.
Robust throttling _requires_ an alternative throttling mechanism that works independent of account information, otherwise I can round-robin between accounts to bypass all throttling.
If you're gonna have that anyway, we're back to "no technical need for accounts".
If they use Facebook login instead of email, how do you plan on getting thousands of Facebook accounts?
B) It's been a while since I last checked, but I don't believe there's anything stopping me from just making shittonnes of facebook accounts
C) Facebook accounts are about 90c each, if you're desperate: https://buyaccs.com/en/buy-bulk-facebook-accounts.php
Accounts are not a throttling mechanism. In and of themselves, they cannot be.