LONDON: A "lack of understanding" is the key reason why UK marketers don't invest more of their budgets in social networks, and was cited by 40% of respondents in a survey by Sapient Interactive as limiting their spending on portals such as Facebook and Twitter.

Overall, 19% of marketers said they did not direct more of their advertising expenditure into social media services due to the lack of tools for measurement or doubts about return on investment.

The fact that social networks are still largely experimental and unproven was also raised by 17% of participants, and 14% said there was simply "too much out there" to make an informed decision.

However, 50% of respondents thought 2009 will be "the year" for marketing on social networks, and a similar number had run a campaign on one or more of these sites in the last six months.

In all, 63% of campaigns run on social networking portals formed part of a broader communications effort rather than a standalone strategy.

Sites like YouTube and Flickr had been used in 62% of social networking campaigns, a figure falling to 59% for "microblogs" like Twitter.

Just 9% of respondents said they thought that social networking was "overrated".

Data sourced from Brand Republic; additional content by WARC staff