I can see lot of new templates for phpld/wordpress coming up these days and going for sponsored links auction.. I am thinking to sponsor some.. but do they really help.. How many will download our template ? Also how to know whether the user had removed the footer links or not ?
well you can't really know that how many users removed footer copyright....but most users don't phpld and wordpress templates are very popular and many people download them, especially if they are available on phpld/wordpress template download sites
Well, if your templates are downloaded and installed and the copyright info is kept, then yes it does help. However, there is no guaranty that your templates are going to get used, let alone the link to your site kept.
Embed the copyright in an image and in CSS. It won't help your backlinks, but it will draw a few visitors. Do this in addition to normal links.