The image below was created using the new Google Trends Websites feature.
Until a couple days ago, to have such a chart i would have to pay for a Comscore report, or rely on Alexa’s data, which has been known to be quite unreliable.

Taking a quick pick at the chart, you’ll notice that Friendfeed is growing, and it’s growing fast having already gained more traction than Jaiku.
It surprised me that Pownce hasn’t been able to create any traction, despite being backed by digg founder Kevin Rose.