Yoomba, a Menlo Park, Calif.-based company that let users send and receive phone calls and instant messages through their email programs, has shut its doors, reports VentureWire — continuing the trend of VoIP consolidations and failures that has emptied a once crowded space (including still afloat Jajah and Broadsoft).

There was a fairly salient flaw in Yoomba’s business model — users could only call others who had downloaded the program, and its market share just wasn’t big enough to make it work.

The company, which has already taken down its web site, had taken undisclosed funding from Global Catalyst Partners and US Venture Partners.