Oct 28, 2010 10:46 GMT  ·  By

Plenty of high profile web startups are starting to fetch very high valuations, despite the fact that they are still private companies with no stock freely available for potential shareholders.

Twitter for example is valued at almost $1.6 billion, based on some transactions, not a huge amount compared to the likes of Zynga not to mention Facebook, but a good figure for a company with very little revenue.

In secondary market transactions, Twitter shares trade for at least $7. Based on the fact that Twitter has issued 225 million shares, its worth comes at about $1.575 billion, as TechCrunch reports.

It is also said that smaller transactions can fetch even higher prices. The $7 figure is for share sales worth $1 million or more. But for those selling fewer shares, the figures can be higher since there are more people that can buy them.

Twitter raised $100 million in its last funding round in 2009 and was valued at $1 billion at the time. This was a big improvement over the $250 million it was pegged at in its previous round, in February 2009, when it raised $35 million.

The company has grown in value as much in the past year, but this can be correlated to the growth in the number of users.

Usage exploded at Twitter starting in early spring 2009 and for much of the first half of that year. The site has been gaining new users since, but at a much slower pace.

The company has been drumming up revenue sources, though monetization is still in the early stages.

Twitter has been introducing a number of specific advertising units under the "Promoted" logo. It first introduced Promoted Tweets for companies or users that wanted a certain tweet to be highlighted for related searches.

This was later expanded to Promoted Trends, a much more visible ad which shows up next to the organic trending topics. Very recently it also introduced Promoted Accounts for those looking to add more followers.