There is an unlimited drive to innovate in nearly any area. And the easiest way to innovate is to copy a concept that has been invented in an adjacent or remote area.

Donations where originally reserved to non-profit organizations (Amnesty, Greenpeace, Red Cross, WNF, etc) to fund their (ideological) activities.

Now you see this donation pattern on a regular basis on the internet. The best example I saw was on a internet site of which the owner exhibited a self development ideology -- acting against the traditional order (society). The owner had just switched from an adsense method to this donation mechanism because the adsense income fell short.

Even though it seems a harmless idea borrowing the concept of donation for a profit business -- which did seem to work in his case -- you might wonder whether you act in line with conventional ethics. In the case I saw, the site owner wasn't really concerned about something earthly as ethics, yet others that follow this example should.

Donations go hand in hand with some kind of an ideology. If there is one you are free to use the concept, both as a buyer or as a seller.

If you have a strait forward profit in mind you are misusing the concept. This is not a problem for the one with the malicious business, they are everywhere. You as a potential buyer should know better. Be prepared before you engage yourself with this kind of businesses. Take a minute and think about the ideology you value.