Of course there are agreements between hotel concierges and the services/vendors they recomend.Do you think any one would take the job if they had to exsist on the measly tips that most travellers give them?
But is that a bad thing-in some cases probably,but in many cases no.
If the concierge reccomends a place,he should be able to reccomend it without concern.If he gets a little thank you from the establishment/vendor so what if it is a good place.
More troubling to me is the placement of "corporate"concierges who have no real knowledge of the surrounding area and simply use a computer program/site such as city search, expedia,pr the like.
There was an article about the outsourcing of concierge desks in hotels to these companies in the NY times recently-very scary and much more troubling than the "referal"system which has been going on for a while now.
How this would work for the Plat.concierge I have no Idea.