In The Clock is Ticking for Joost Techcrunch highlights why Joost is in trouble - it's the technology.  If all you have is Technology, then you often, don't have much of anything:

"..Sometime in the next few months, Adobe is expected to incorporate the H.264 codec in all Flash players with the general release of Flash Player 9. You can already download a beta version from Adobe Labs. The H.264 codec is part of MPEG-4 and is the codec that Apple uses to compress all of the video downloads on iTunes. Once H.264 is part of Flash, the quality of streaming video on the Web will roughly double at current bandwidth speeds. That means YouTube videos will look twice as good—and those will likely remain on the low end in quality.

Every video site on the Web (and quite a few that are still in stealth) is just waiting for Flash Player 9 to be distributed widely and become the new standard. That will allow them to launch their own full-screen Internet TV services with video streams that are just as good or better than Joost’s, and that will require nothing more than a regular browser to watch."

I think real value comes from features and attributes that you can't copy easily - but that's difficult to have if the main offering is technology.