Take away a freebie and people will hate you.
The latest EconTalk podcast relates a story of people who harbored a grudge against the Red Cross for decades. What did the Red Cross do that was so bad? They sold doughnuts at cost.
The Red Cross had given soldiers doughnuts for a while. Then at some point they started charging a nickle. They were not making a profit, only selling the doughnuts at cost. And they only started charging because the U. S. Army asked them to. Even so, some veterans and their families remained angry about this for many years. To this day, some Red Cross workers bring free doughnuts to meetings trying make up for hard feelings.
If you give away something but make it clear from the beginning that it’s only free temporarily — a free sample, a trial version, etc. — then you may charge money later without causing resentment. But if people ever get the idea that your product will remain free, they feel entitled to it.
If Facebook, for example, decided to charge even $1 a year for an account, they would lose millions of members. People would burn Mark Zuckerberg in effigy. Presumably they could have charged $1 a year without criticism when they started. But since the service has been free, they can never charge for it without creating enormous ill will.