How to AVOID Guests TAKING Centerpieces??

hi,

You girls are awesome.

I want the kind of centerpiece that ends up sorta looking like a ball of flowers is hanging over each table.

I think I will have to rent that metal centerpiece??? My mother says that I have to work it into my budget b/c people will TRY TO TAKE them home. I understand guests taking home centerpieces, but will they try to take this one???

The hall has no incentive to prevent this from happening, b/c it is from an outside vendor.

Thanks,
Any ideas with that ball of flower ideas would be awesome too.
XTINA