Interesting idea but for the first one, what would stop people from programming bots to know the answers in advance? The second one would still require a lot of work with the sheer amount of posts and new registrations. The subject of spam and newbies is definitely a hard subject to solve. Maybe until we adopt something like biometric logins (could cut down on bots and duplicate accounts) in the mainstream but I'm sure someone will find a way around that too.
The question bank is more questions than you need so the bots would have to sign up many accounts before they saw all of the questions. Also you could use a captcha or something for access to the test.