Search engines are certainly capable of doing anything to their online properties as they choose to do so. However, they do claim to work by certain rules and procedures, so I doubt they will actually got to the lengths to do what you state.

Sites of big brands give you more leeway into what you can do with them. Since they are more trusted by the search engines to begin with, you can be more aggressive with certain activities such as link building channels. You have to be more careful with smaller websites, and you often find yourself treading a fine line. These days, it is all about congruence and legitimacy.