Is Twitter planning an initial public offer? Well not at the moment. Yet the microblogging site a valued at a whooping $7 billion.

Pegged at around $1 billion in 2009, Twitter's values last December was $3.7 billion. Around this time Kleiner Perkins Caufield & Byers invested $200 million in Twitter, and its book value zoomed to $6.8 billion.

Twitter follows a unique mode to raise.

Instaed of following the much traded path of IPOs, Twitter raises money from private investors.

The growth in Twitter's value is partly due to the rise in its advertising sales, which more than tripled to $150 million this year.

Interesting this is hardly anything compared to Facebooks's ad revenues, which stood at $1.86 billion in 2010.

The fast-paced Twitter also plans to target 1 billion users.

Rumour is rife that Facebook, which has more that 500 members worldwide plans to go for an IPO by the end of 2011.