Re-read my prior post. I just discovered a new flaw in Iota.
[1] Make sure you understand the implications of this. Seems to me that Iota's mining can be outsourced to ASICS, thus Iota's mining will economically centralize same as for Bitcoin!
There are no fees in Iota to encourage centralised mining. The reason they have this non-signing policy is because transactions can become orphaned, therefore unless they expect the payers to continually monitor the tangle and re-send any orphaned transactions, 'others' must be required to do that job for them.... It was never clear to me what incentive there is for anyone to redo that work, though.