Why? Like the article states, people don't like giving out their email address. Why reinvent the login interface millions of times when you can just use one. Google, Facebook, Twitter (etc etc) already provide those interfaces, so use them!! Hell, I've turned away from betas just because their sign up form is too annoying.
However it'd really depends on what the offer is. This is an indirect suggestion to do some marketing 101 ;)
I think this is the main point, if you have a way to let people know how long the queue is and where is your position in the queue, it might actually work.
On top of that, I've had it happen twice that I did what I was supposed to, and I did -not- get access.
So I've really, really soured on the whole thing. At this point, I only pay attention to people who have an actual product that I can actually use. Every else gets ignored.
My suggestion for new startups is to put an information-rich page with screenshots and explanations how that idea came to life, how it will change your life, etc - of course if your goal is to get people interested and to signup :)
To be honest, Launchrock are just being ridiculous at this stage. They actually seem to be going backwards. I signed up for their beta over a year ago, still nothing except several "coming soon emails".
But if you are a startup founder, remember the reason you see these viral sign up forms everywhere is because they work. You'd be silly not to offer the opportunity w/ your visitors because a small percentage will indeed share with their friends. Of course, that percentage is going down as people get fatigued or get burned by other startups that don't follow through.
The lesson for startups is that put a teaser on the sign-up form so people know what they are getting excited about.
