There are some red flags in Snapchats IPO filings - massive losses, decelerating user growth, 0 voting rights etc. So I personally have doubts about demand for the $25B valuation.
It is a massive scam. In my opinion, Snapchat is not even worth $5 billion. Investors are ignoring the risks which are associated with snapchat. Applications such as Spanchat rarely remains popular for more than a couple of years. After that, they tend to get replaced by some other application. Look at what happened to Orkut and Myspace.