For me, the key point here which absolutely nobody could argue with is the number of people out there running "social media masterclasses" who have little or no online presence at all. It amazes me that anyone would sign up for training with someone who has no Facebook page AND has tweeted five times in 2011 (all links to their own website) and only has their name and job title on LinkedIn - but I see it all the time.
Once you go beyond that, I think you're on shakier ground. If there's anyone in the industry able to keep up a perfect presence on all the key sites plus a few niche extras, AND keep up with all the new developments AND actually do any work for clients, I've yet to meet them. So it's always going to be possible to pick holes with a little digging around!
I guess it's all a symptom of low levels of buyer education in the digital marketing space - a quick glance at the immediate appearance of the "number ruse" in so many of the above posts shows that even those with some knowledge are still falling for this. I could set up some software to get myself 100,000 Twitter followers, or buy them, within a few hours. All that would prove is that i'm a charlatan who likes taking shortcuts to impress the uneducated...
Mic's comment is wonderfully honest - the truth is, nobody can be an expert in all aspects of digital marketing, and to deliver value we just need to be one step ahead of our clients. I've not been in DM for 5+ years, but that doesn't mean I can't deliver a lot of value to someone who doesn't know how Facebook works or where to start with buildng a strategy - and whose budget wouldn't stretch to a big-name "expert", even if they were in a position to benefit from the level of knowledge they may have!