People who feel they are entitled to everything for free on the internet. For example, I have a website where I give away a lot of graphics and other such stuff, and I have written a great deal of useful content for free. Due to Google's recent shenanigan's I had to redo one of my websites that was 12 years old to make it more mobile friendly so it wouldn't get penalized.
A long time visitor and client of mine had the audacity to write me a scathing email that my new site was not only not as pretty as it used to be it was no longer serene and was now just "sad". She also admonished me for having ads on my pages (I had ads on the previous version too) it went on and on and was very insulting. I promptly told her "you're welcome for all the years of free content and services you have been taking advantage of" ... then she apologized for going too far...
I think there is this heir of entitlement some people have - they think that everything on the net should be free for the taking and fail to realize that behind all of their free apps, games, software, images, recipes, articles etc. they enjoy are human beings with feelings who are working very hard hard to provide these resources that they use for free.
My advice - say thank you once in awhile to people - or at the very least don't ball them out for not giving you all the free stuff you think you need the way you want it.... do it yourself if you can do it better people! :)