I don't think getting permission was ever part of the protocol with graffiti artists.

I don't think you are getting the whole 'street art' thing, hugh3.

I guess you are also wondering where people collected all of those permissions to share media on Pirate Bay, too?

Poor analogy.

It's only poor if you don't consider intellectual property "real" property.

If you do, it's reasonable.

It's the obligation of the person choosing the analogy to pick one that connects with the audience.

It's supposed to make the communication simpler, not to add more burden.

Hence, it was a poor analogy.

I doubt the business would appreciate you blacking out their Banksy:

http://www.telegraph.co.uk/news/uknews/1549107/Banksys-30000...