Advertising has so thoroughly co-opted enthusiasm and twisted it to serve its commercial purposes that genuine enthusiasm has come to seem extremely suspect. So it becomes more and more difficult to make recommendations that won't be taken with a grain of salt, that won't have the other person wondering, Hmm, is he just repeating some hype he's heard? Has he been brainwashed? Will this just be one more overblown thing that will ultimately not live up to expectations, like everything else in the consumer world?
People want to be infected with enthusiasm, but at the same time we need to guard against contrived excitement, bogus word of mouth, covert agendas and so on. But the trust that allows us to accept enthusiasm as genuine, which has all but disappeared from the public sphere and from discourse in the media, is itself slowly being commercialized with the proliferation of social networks and Internet advertising that is generated by the collective proclivities of voluntary peer groups. The advertising takes advantage of one's eagerness to affiliate and uses that as a way to infilitrate and begin generating new "needs," to begin defining the terms of group inclusion along the lines that serves the advertiser. At first the group will simply be collectively familiar with certain commodities, then the familiarity may begin to bleed into ownership -- everyone in the group just seems to be into the same things that happened to be featured in ads targeted at the group. It will seem that everyone in the group already liked the things advertised, so the ads won't seem obtrusive and the whole question of outside influence will become a meaningless chicken/egg debate. In that way commerical interests hijack the fragile trust between friends, and make the substance they inject into that relationship the very food the relationship feeds off of to sustain itself. We have probably decided long ago as a culture that we don't have any problems with this.