Hey, I think I got the answer myself. Actually I opened Lightbeam yesterday for the first time, and it was not showing any website tracked over there. Yesterday I tried it 3-4 times, it didnt show me any websites tracked. But when I opened it today, its showing me tracked sites, that too since the day I installed it.

The day I installed it, it was tracking fine... but since the next day it has stopped functioning.. i mean tracking... Any one knows what happened or how to get it working...??

try reinstalling it !! it takes time to integrate itself !! it might happen so that while integrating itself the process remained incomplete !

Okay... as suggested on fb... it worked after restarting firefox...

For me, the number of sites visited stayed 0 until I paused blocking in the Ghostery's Add-in... I made some changes in the settings there and a nice Daily Graph is showing now!

Lightbeam on Mac OS 10.6.8 - Firefox 25.0.1