Every year the company my BF works for organizes a Christmas concert for clients and potential clients: everyone in his office must personally issue invitations to his or her own clients. Bringing friends and family is encouraged as long as we are told in advance how many seats they'll require: the company usually rents a theater and there are only so many seats available (and that's without getting into safety issues).
This year we had two international artists playing an opera* recital - not to everybody's taste, I'll admit it, but it was specified in the invitation. It's entirely possible some people had never heard a single opera aria* in their life, but still they would have known it was opera and not, say, waltz or rock'n'roll.
Well, after the concert a few people walked up to their contact and complained about the show. Not that there were any problems with the performance, they just didn't like the music.
Maybe I'm being too sensitive, but I found that pretty rude.
Yes, the concert is, in the end, a marketing ploy. The audience might not have paid for a ticket but did, in a sense, pay for the concert by making business with the company. But the company doesn't have to organize the Christmas concert: it's just an added bonus.
If they didn't think they would enjoy it (again, the invitation said it was opera*), they didn't have to come. And if they thought they'd enjoy it but then didn't, I can't understand why they'd go and complain, especially because those who issue invitations are not the ones who organize the concert.
* = it wasn't actually opera, just trying to disguise the event in question.