Well, to begin with, some web presence is better than none.
Chances are that other things you've done on the Internet will show up if someone searches for you. Ideally, there would be a way to have people remove old, irrelevant references. But in the decentralized world of the Web, there's no single repository where you can update your information. Part of the reason for the advice to establish a web site and blog and tweet and friend and circle is that new web activity will push old web activity down in the search results.
So why do we have to worry about being authentic?
Well, in simple terms, no one likes a salesman--or, more accurately, someone who appears to be nothing more than a salesman.
But there's something more going on with the Internet than a simple test of your ability to go for more than five minutes without shouting, "Buy my book! Buy my book! Buy my Book!"
The Internet is a slow, not entirely perfect, truth filter. Over time everything on the net is exposed for what it really is. Flash and SEO (search engine optimization) techniques may work for a while, but substance will win out in the long run.
So how do you do authentic?
Bob Mayer said,
"The first author we brought on board besides my books was Kristen Lamb with We Are Not Alone: The Writer's Guide to Social Media. ... And we incorporated the things she espouses in the book; the primary one is have your content first, before you start blasting things out on social media."
Authentic is about substance over form.
Like the Boy Who Cried Wolf, it's actually not that hard to get someone's attention. What's far more difficult, and hence much more significant, is keeping someone's attention. If there's an author whose books you buy whenever a new one comes out, it is because of the author's antics or because they've consistently given you a good reading experience?
Content is how you do authentic.
Image: Photography by BJWOK / FreeDigitalPhotos.net