The manufacturer tell you that you can't use a spin balancer even with the bead in it. Here is from their website:
Q: Can I put the tire on a balancer to see if it's working?
A: No. Dyna Beads operates on physics principles, and requires the tire assembly to be in motion against a road surface to detect the exact counterbalance position. An electronic balancer has a solid, fixed mount, and does not allow the tire to react to imbalance.
What do you expect them to say? Of course they'd say that! Again, I have no personal skin in this, but that logic doesn't hold. The beads don't detect anything, they are flung out against the inside of the tire as a result of centrifical force, and I'd guess they would go to the point that is furthest from the center axis - which very likely may not be the lightest section of the tire. Then as the tire rotates, I would think the area of deflection would bounce the beads constantly. I sure would like to see a demo of a transparent tire to view what's really going on in there.
To be honest, I think most riders can't tell a tire that's less than an ounce off balance. As such, I have to lean towards MCN's side on this one. I don't think the beads necessarily hurt anything, but they sure can't be as accurate as a good spin balance. However, it is true that a good spin balance will eventually go off as the tire wears, so that needs to be considered.
Frankly, if someone did a test using a road force spin balancer, that would put the question to rest for sure. There's absolutely no way the bead guys could dispute that test.