while exploring Flock I ignored one most important feature of browser its security & vulnerability response. As Flock is based on firefox it has many added features plus all bugs & vulnerabilities of firefox.
Flock team says they has 2 weeks gap on security vulnerability i doubt on it & i believe they are way behind in fixing security hole. although 2 weeks itself a lasrg gap specially when attackers got all knowledge from Firfox bugzilla.
I realize this this flaw when i got complain of spam from my face book & twitter account . That indicate that my system got attacked by some malicious program using some firefox vulnerability. & eventually use Flock as weak spot.
Finally i uninstalled the Flock & get back to firefox.