Search the following term on google.ca "Palace On Wheels", See the top 2 PPC results. What a heck just by changing the domain extension .com and .net one is doing ppc for both. Isnt it spamming or for PPC there is no spamming at all.
Now their .net domain is going to not found but in the morning that site was live as well and both sites are having PR. Well so if one is paying good amount on PPC he wonnt have to worry about spam, its seems so by this example. I guess bigger corps can completly rip off smaller one on PPC like they can have same site with different extension like .com, .net, .org. co.uk and so on and do ppc for all sites with similar keyword so that all ppc results are of their own one.