In the following video, analyst Brendan Byrnes speaks with Fool contributor Andrew Tonner about Tesla and the electric-vehicle market as a whole. Tesla has done a great job executing lately, and its stock has absolutely been on fire over the past few months, rising over 300% year to date. 

The Model S has proved to be a phenomenal car, but longer term, Brendan thinks that a lot of the success of the company will depend on Tesla's success in tapping the mass market for electric vehicles with a vehicle under $40,000 or so. 

Ultimately, this is not a company that Brendan is betting against right now, but at a $15 billion market cap, there's just not enough margin of safety in this stock for him to jump in. See the video for more details.