What's the correct way to implement website/list with crowdsourced content?

I've seen some people start out their website using a spreadsheet which was populated with crowdsourced data, yet I never get how they prevent it from filling up with unwanted/spammy data. I'm trying to do something similar to this but with an actual website (no spreadsheet) and I don't know whats a good approach towards filtering unwanted data.

What I'm thinking so far:

Make an submission with approval system for every data modification.
Let it run freely and filter by hand afterwards.
Let only registered users modify the data, register their modifications in a stack and then rollback the stack when a spammy user is banned.
Make a voting system that keeps the most upvoted modifications.
Populate the entire data myself.

Has anyone done this? If so, what was your approach for filtering unwanted data?