Trollestia is now canon · 5:39am Feb 5th, 2013
Here's the text from one of the quests in the MLP Gameloft game*:
I love to pull pranks! It's all in good fun, and Pinkie Pie looooves to have fun! Let's give Ponyville a few giggles! It's totally what Princess Celestia would want!
Proof that Trollestia walks among us!
* "My Little Pony" on Android, or "My Little Pony: Welcome to Ponyville" on iOS