I think looting from any random shop is not acceptable as the owners are innocent people. However, if a major corporation doesn't pay it's taxes or do something like Nike- deliberately employs workers in countries where there are no workers' rights. I think the question really becomes which variable is more important? Is Google paying 1% corporation tax in England more more acceptable than their right to property? If so, you do not damage their headquarters. Again, if protestors come across Google HQ (which they actually won't because google HQ is pretty much a shack in a country which doesn't pay much corporation tax and which employs no people) then if the moral obligation to punish immoral people is more important than right to property, protesters should be able to smash it up to some extent.
Looting is never an acceptable protest activity. Looting involves destroying and stealing property. This makes business owners less likely to open businesses in neighborhoods that are prone to looting. Furthermore, it makes protests look bad - even when there are legitimate issues being raised - most see looting as a crime.
No, looting is not an acceptable protest activity in the face of social injustice because it takes away from the true problems we face. When people see looters on TV, they do not think of them as activists. They are simply people trying to make a profit during troubling times.
Looting is unacceptable, regardless of what may have fueled it. Although anger over what is deemed injustice is understandable, looting has no place in a reasonable response. Instead, looting becomes a way that some may choose as an outlet for their anger, but damaging property and stealing from businesses is completely unrelated to the root issue.
Looting is not a good idea. It hurts innocent people and members of the community. But that does not mean the looting actions of a few people should outweigh the peaceful protests of many people. The amount of looting going on has been widely exaggerated by the media, who are trying to boost ratings.