(Edit: I actually read the article after my post and saw the section about Benchmark Capital's $13 million investment. The rest of my comments still stand...)
Now if you meant they have built such a large following that a buyout is inevitable, and/or they stand to make a lot of money by introducing a business model into the equation, then I'd agree. However, that does not change the fact that the owners are incredibly greedy not to accept a $3 billion cash offer, especially considering the fact that there's no guarantee they can come up with a viable business model at all. Now that they've turned down an arguably hugely inflated offer, they may have made a huge mistake in the long run.
Let's not forget that Snapchat isn't exactly a difficult product to clone, and the only thing going for them right now is user numbers. If they introduce a poor money-making mechanism into it, users will not hesitate to flock to the "next big thing" instead of forking over cash or dealing with intrusive ads.