A gathering of Raven's is also referred to as an "Unkindness"
How cool is that?
My parents in Winnipeg have a couple acres just outside of town. The Magpies and Crows so cool to watch. They outsmart the cats and squirrels NP.
The only issue with keeping a crow / raven as a pet would be the mess they would make. Seed eating birds = small craps. Scrap / fruit eating = projectile evacuating of the lower intestine.