After getting a copyright strike for doing a reaction to a fanwork Alex Side received a copyright strike and has decided to no longer making reaction videos...I hope there is a way to resolve this kind of issues, because I'm sure that we can. It may not be as easy as that but I think we should do our best to respect the wishes of the content creators who work very hard on their content.
Alex Sides video
https://www.youtube.com/watch?v=4E3uie4Otb0

The following reactors have made several videos to create a MLPReactList of MLP Content creators and their stance on Reaction Videos. I think this is a great idea so please spread the word with #MLPReactList
MLPReactList - https://docs.google.com/spreadsheets/...
BronyMonster's vid: https://www.youtube.com/watch?v=Fl0ww...
PieDisliker's vid: https://www.youtube.com/watch?v=gSMwm...
8Feet's vid: https://www.youtube.com/watch?v=O_A0m...