I didn't see it mentioned in the blog post, but in the press conference Z said they are not monetizing deals yet, and have no short term plans to.
EDIT: I removed a point saying I didn't think these would be more interesting than what Yelp does until they start to monetize. I think that's too strong a statement.
Except that they have such a huge existing userbase compared to Yelp (both in terms of end-users and businesses who are aware of them, and likely use Facebook themselves already).
That's because you open yelp looking for NEW places to check out, fb/4sq is for the places you already are or friends are. People discovery vs venue/place discovery
EDIT: I removed a point saying I didn't think these would be more interesting than what Yelp does until they start to monetize. I think that's too strong a statement.