That's the ToS department. The reason you see that happening is because the links you are posting are not allowed on free hosted wordpress.com blogs. Read the types of blogs allowed and not allowed page very carefully.
In a nutshell no blogger initiated advertising, retailing or reselling the work created or services provided by anyone other than yourself is allowed on free hosted wordpress.COM blogs. E-commerce transactions via shopping carts and the like cannot be conducted on free blogs from and being free hosted by wordpress.COM
If you have any further questions about advertising and/or affiliate links and/or ecommerce on a free blog from and being free hosted by wordpress.COM please contact Staff directly using this link when support opens tomorrow. http://en.support.wordpress.com/contact/
If you do require an ecommerce site, advertising and/or affiliate links you can hire a web host and get a free software install from http://wordpress.org Refer to > http://support.wordpress.com/com-vs-org/