Callie Oettinger has a nice take on the flaws that are inherent in the traditional PR/Marketing model: it's all designed to sell to the wrong audience. She's writing about books here, but the same thing applies in software:
Traditional media outlets have never covered even a dime in the dollar of books published each year. Everyone wants in, but there’s not enough room. And even though specific genres have never received equal coverage from traditional media outlets—military, science-fiction, and romance come to mind—many of the publishers and authors of these books continue traditional pitching, hoping something will stick. Why? Because that’s what’s always been done.
Very true. Consider software now - do "decision makers" actually evaluate the tools that developers or end users use? Of course not. Heck, most of them don't even look at such stuff - they have staff for that. Sure, at high levels, with truly expensive software, the golfing relationship between the (insert vendor here) and the CEO matters. For everything else? What matters is whether your product's value proposition reaches the right audience: the users.
Go back to books again. Pre-internet, all you had were book reviews from prestigious outlets (like the NY Times), and the advice of local booksellers, who had some notion as to what was coming out, and what might appeal to you given your tastes. Now? Now there's Amazon recommendations, book lists on blogs (I've picked up a ton of stuff based on posts from Glenn Reynolds, for instance) - and so on. The problem with the traditional outlets is that they are at least one step removed from the real audience.
Which takes me back to software - the "decision makers" are also removed from the actual use, and their only point of evaluation is price - it's the only thing they have. If you sell on that basis, and can undercut everyone else, then sure - bypass the users, and get into the race to the bottom. If that's not where you sell, then you really, really want to be active where the actual users live - because it's the only way you have to stand out from the crowd.