I don't see why. SNAP hasn't really figured out how to make money and their features were easy to copy (and copy better) in Facebook's properties.

MongoDB is far longer established, has a large enterprise business and likely has a sizable cloud business. These are not "features" you slap onto another product and then simply have users come flooding to you. No, databases are pretty critical pieces of infrastructure.

As long as the business is solid this IPO should work out well, IMO.