> But... I wonder if I add this free service
>, will I kill any possibility of attracting a
> paid banner advertisement?
Probably not. Content attracts TRAFFIC, and TRAFFIC attracts
>If I add this free feature to create more content
>for my visitors to refer to, why should someone pay
>for advertising when everyone else is getting it for free?
Perhaps limit the free links to academic and non-profit sites,
and expect any commercial entities to pay. My evil twin runs a
site for books, and only dead authors get free listings. All
others must pay, no matter how famous or deserving they claim