Paying for services is not necessarily enough
There is a meme running around the Internet that if you don't pay for the services you use, you're a sheep. The problem with this is that we have plenty of demonstrations that even paying for services is not necessarily good enough to insure you won't be turned into a sheep.
My personal demonstration of this is Flickr. I've paid for a Flickr Pro membership (and felt it was worth it) for years, but then Yahoo changed the account structure this summer. Flickr's new price of $50 a year to not be shown ads is well above the current renewal rates for ad-free Pro accounts, and on top of that they no longer offer new Pro accounts. While they have not come out and said it outright, the new pricing to not be shown ads makes it clear both that Pro accounts were not enough for Flickr and what Flickr's new business model is. And it's not sustaining themselves on my money, certainly not at the discounted rate I'm paying now and perhaps not even at full price. Flickr apparently wants (and perhaps needs) sheep to be sold to Yahoo's real customers, their advertisers.
(I suppose that this too is part of Flickr knowing their focus.)
Well, you may say, of course paying for things by itself is not good enough; you have to pay people who are building a sustainable business. The problem with this advice is that it's very difficult for me to know if your business is really a sustainable one or if you're just papering over the cracks for now. There are signs and indicators, such as the presence of free accounts, but they're far from definitive.
(Not even past success makes the future certain, although it makes it much more likely.)
Does this matter? Maybe. People who are determined to try to pay for sustainable businesses will keep paying, because for them it is partly a moral issue. People who feel that they are getting current value for money will also pay for service (I don't regret paying for Flickr Pro and I felt I got my money's worth, even at the moment). But I do think that this exploitation of even paying customers makes it harder to argue that you should pay for everything when just as good free alternatives exist. If you're likely to be exploited one way or another, you might as well not pay for it.