Is this good business practice?

In the last few years, I have seen some sites such as directories, blogs, top lists, tgp's, etc. that build their traffic on recip links and bookmarks suddenly change the site into a paysite....and of course capitalizing on all those inbound links, bookmarks, brand, built under the previous incarnation of the site..

And, it appears that the switch to a pay site model is usually done without notification to those inbound links that they are switching their site over to this new format..

Is this a strategy that is ethical to pursue?

Is it good business practice?

It is fine with me. Things change over time. If the site owner wants to change the site to a paysite, you will lose your link back, and you can remove the link from your site at that time. I think of it as the same as a site vanishing or converting to a "domain for sale"/advertising site...keep on top of it if you want.

if the paysite has more to offer, then yes its ethical. more and more webmasters are finding the benefits of paysites

jub did that and they removed a bunch of listings that i had there too i was not happy about it but i just took there links off my pages