Maybe as shady as any other 'man in the middle' deal - for instance insurance brokers, realtors, etc
So many websites do affiliate marketing in some form that you can't just throw them all in a bucket of 'shady'.
If you do a blog post comparing slicehost to linode, and have your signup links in it, that's affiliate marketing. Nothing particularly shady about that.
Moreso - I worked with a direct marketer / affiliate marketing agency for the first 8 months I held a full-time job; they were primarily in lead generation, of course, and got most of their leads from other lead generation companies, who got theirs from still others.. at the end of the road, those leads were coming from people paying bottom dollar for half-baked PHP apps. And by the time those leads actually reached the entity (online education, in our instance), they had changed hands three, five, and sometimes more times.
At each instance, of course, their personal information passed through companies who had no moral qualms about holding onto those leads and passing them off to a future client as new.
So many websites do affiliate marketing in some form that you can't just throw them all in a bucket of 'shady'.
If you do a blog post comparing slicehost to linode, and have your signup links in it, that's affiliate marketing. Nothing particularly shady about that.