youfoundjake - 7:28 pm on Mar 9, 2007 (gmt 0) You may not get full credit for all the links to you, but you shouldn't get dinged for it.
Purchased links are generally frowned upon by the major search engines as its indicitive of SERP manipulation. They like natural IBLS and have ways to determine if links are payed for.
Concerning natural IBL's, where you aren't paying for the sitewide link, as long as you don't link back to the site, it should not affect yours negatively.
If it did, then it would be to easy to mess with your competitors rankings by just doing a sitewide link to them from your site.
You may not get full credit for all the links to you, but you shouldn't get dinged for it.