Facebook's purchase number is staggering, but the acquisition, in theory, make sense. Zuck's own attempt at a disappearing messages app, Poke, bombed earlier this year. The app not only sucked, no one trusted Facebook with their sexts. From the WSJ:
Facebook is interested in Snapchat because more of its users are tapping the service via smartphones, where messaging is a core function. Facebook has rapidly increased the share of its revenue coming from mobile advertising, but said last month that fewer young teens were using the service on a daily basis.
Sources told the WSJ that the 23-year-old Spiegel will likely not consider an investment or acquisition until early next year. Spiegel feels that Snapchat's growing user base will justify a larger valuation.
350 million messages are Snapchatted each day—and investors have, before Facebook, taken notice. Tencent, a Chinese investment company with stakes in major Asian messaging services, is vying to lead a group of investors to pour into the company $200 million on a valuation of $4 billion. That's more than Facebook offered (after originally offering $1 billion), so it's not inconceivable to think a higher valuation could come in.
Of course, there's also the deal of that court case: Right now, Spiegel finds himself fighting his former friend and frat bro, Reggie Brown, who he forced out of the company before shuttering him from equity. Brown came up with the whole concept of a timer and disappearing messages. (The concept that makes Snapchat Snapchat.) He could take, like Eduardo Saverin before him, a good chunk of whatever money Snapchat makes if it's soon acquired.
For my money, this saga continues to be the most interesting in tech: A 23-year-old guy spurning the offer of an online god who boasts an eerily similar backstory. Snapchat's Social Network might as as well be a spinoff.