Snapchat is on at least two companies' “most wanted” lists. Question is, should it be on yours? If you haven't heard of Snapchat, it's a photo-sharing app that allows users to send photos that disappear forever after up to 10 seconds. Its price has been soaring. From a valuation of $800 million this past June, Facebook (Nasdaq: FB) has reportedly made an offer of $3.5 billion. And China's Tencent Holdings (0700.HK), $4 billion.