The website 20cogs.co.uk (also known as 20cogs.com) is owned by Submission Technology, Ltd in the United Kingdom. It allows users to sign up and earn money for completing specific offers, deals and surveys. Your personal information is not sold to third parties and is a legitimate business with over 300,000 members.
Please ignore the other user who has blatantly lied about 20cogs. They do not sell your personal information; they also state that in their Privacy Policy. Also the listings on job sites are likely to of been posted by affiliates of the company.
I would also like to point out that his statement "It can take you years to reach £400" is total rubbish too. I personally managed to earn a little over £200 in under 45 days.