I asked Hanke the standard question about maliciousness but in a very specific context. The hypothetical we discussed is a competitor swapping out his or her phone number for that of another business. For example, local Florist A ranks better and is getting more calls from Google than Flower Shop B. So Flower Shop B, having cleverly discovered the open-editing capability, replaces Florist A's phone number with its own to siphon off calls from its competitor.
Hanke said that all the changes are recorded and preserved in the system so they can be tracked and observed. It's also the case that users have to register to make any changes, which creates a further disincentive. He added that changes are monitored and moderated internally. The malicious competitor would likely be caught under those circumstances.
'Would likely'? Time to add Maps listing patrol to our daily duties.