For those who have lived their whole lives under a rock then it might be useful to look up these terms:
astroturfing
undercover marketing
stealth marketing
guerrilla marketing
viral marketing
Many companies use these things and especially with
astroturfing, undercover marketing, stealth marketing you may never really know -- although many people might have reason to be suspicious.
By the way, the basic ideas aren't really all that new. Politicians and their staffs have for thousands of years made use of anonymous/unattributed leaks, leaks through surrogates, etc. to let information out, put out disinformation, put up trial balloons, etc. Internet forums and social media these days are especially hot among the politically minded people. Sometimes the person receiving the leak never even knows that it is an authorized, intentional leak.
It has also been pretty common for probably centuries for some politicians, writers, business people, etc. to either use a false name or a surrogate to write complimentary letters to newspapers and other publications or write critical letters about an opponent. These days on Amazon.com there is sometimes the problem of the writer of a book or his friends writing great reviews to his book or to writing bad reviews to someone else's book. I am sure Amazon tries to delete stuff they are suspicious of, but it is not likely that they catch most of it.
None of us know what non-conventional marketing techniques Sony and other companies are using in the 21st Century, but it is very naive to think these things don't exist or that a huge corporation doesn't know about any of them and may not make use of them sometimes along with the conventional techniques. But, yes, some people are very gullible, thus the famous quote:
"There's a sucker born every minute." 
