It seems that you can only disable your account, and your data will be kept forever on their servers, which is not good at all.
Anyway, to disable your account, make sure you are logged in.
Then go to http://www.flirt.com/myaccountmanagement.asp
Click on the “Remove Account” link in the “Account” block.
If you decide to restore your profile, just log on to the site again.
URLS:
http://flirt.com