Livemocha also allows Rosetta Stone to bolt on products in a lower price point.

FORBES: Rosetta Stone Acquires Livemocha And Expands Its Reach In The Cloud

Other popular video clips viewed online included German diver Stephan Feck's 'zero point' dive, Cuban pole vaulter Lazaro Borges' pole snapping mid-vault and Usain Bolt's performance in the men's 100m final.

BBC: Serena Williams