I've noticed two problems with the arc reactors:

One is that enemy arc reactors can power your bulk wireless crystals, and your bulk wireless crystals can power enemy structures. The context of this is that I raided a base and destroyed all of their arc reactors only to find all of their turrets still powered. There was a different tribe nearby. I raided that tribe and destroyed their arc reactors, and then the turrets of the original base finally powered off. I have also been in scenarios where I have accidentally powered enemy turrets that were offline by placing a crystal nearby to power something of mine.

Two is that if an arc reactor runs out of fuel the bulk wireless crystals it was powering will refuse to be powered by any other source, even if there are other properly fueled arc reactors in range. The context here is that I had an arc reactor hidden in my base and forgot about it because I had placed so many back-up arc reactors all over my base. When it ran out of fuel the majority of the base lost power and the only way to get it back was to either remove that arc reactor or re-fill it.