I think he may have meant not making a habit out of $1bn acquisitions of companies with lots of users.
"This is an important milestone for Facebook because it's the first time we've ever acquired a product and company with so many users. We don't plan on doing many more of these, if any at all" [1]
"This is an important milestone for Facebook because it's the first time we've ever acquired a product and company with so many users. We don't plan on doing many more of these, if any at all" [1]
[1] http://www.facebook.com/zuck/posts/10100318398827991