[pjc50]

The worst cost of documentation is that it often generates extra work for you in terms of complaints and updates. Not always reasonable ones, either. More than a few personal projects have been taken offline because it's too demoralizing to give things away and get negativity back.

[nicbou]

I offer them a refund. It gets the point across.

[avgcorrection]

Considering that some blog post about something can remain relevant for years—as opposed to some off-hand tip given verbally—, it is definitely difficult to just share knowledge in a way that cost you next to nothing. You could give some great advice that works now. But doesn’t in two years. And then it might be counter-productive.