When you have enough companies trying to ride the viral invite/closed beta wave with closed betas for a business to specialize in viral invites, it’s time to pull the plug. Artificial (or real) scarcity imposed by marketing as a promotional gimmick is no reason to spam your friends, folks.

This morning I reached my personal tipping point for the viral invite gimmick. I was already well poised to boil over after the U.S. launch of Spotify, but this morning another service (that I won’t encourage by providing a link or name) put me over the edge. Not only is it another bogus “invite only” closed beta, but the company promises faster access if you offer up email addresses for at least three friends.

Spotify had an easy sell with me before pulling the viral invite stunt. As most of my friends know, I’m a hardcore music junkie. My CD collection is overflowing my CD shelves, and my MP3 collection (all legit) by far takes up the most room on my hard drive. A music service that gives me the opportunity to discover scads of new music? Sign me up! Better yet, I’d heard great things about Spotify from my friends overseas, and was eager to get signed up for the service until the company decided to get cutesy by exploiting the demand for Spotify and just throttling users to try to push people into signing up for a paid account straight away.

Granted, Spotify just put a new spin on a time-honored tradition for new Web services: Generate buzz around a service by setting up an artificial scarcity. At least Spotify isn’t trying to force excited users to cough up the email addresses of three unsuspecting friends or co-workers.

You can blame Google for making the viral invite so popular. But the company also gets a bit of slack, given that it’s next to impossible for the search giant to do anything unobserved. When Google first used invites for Gmail, the company was doing something fairly new (at the time) by developing a new service in the open. With Google+, I think Google also has some legitimate reasons for limiting sign-ups while they make changes to the service and scale it out. But these are the exception, not the rule.

This morning I caught wind of an interesting service and went to check it out. It’s a service that (allegedly) provides a visualization of your profile on LinkedIn. They claim that they’re providing “free premium accounts” to the first 10,000 sign-ups. Sign up, and they promise to speed up your invite if you just spam three friends with their service. Apparently, this isn’t just an annoying trend – a startup called LaunchRock is actually providing a service that provides the landing page and demand for email addresses.

A true closed beta, one where a developer sends around invites to close friends and such, is fine. But the companies looking to “go viral” when they’re not yet ready for prime time are profoundly annoying. Worse are the startups that want to harvest the contact lists of easily excited users.

I’ll be impressed when a service launches fully formed (at least a 1.0 version of “fully formed”) and respects users enough not to suggest that they spam people who may or may not care to hear about the service. While it’s nice being on the cutting edge and all, I’d rather hear about services my friends are using happily enough to recommend without prompting. Seeing an unsolicited invite in (one of) my already crowded inboxes is a bad way to make a first impression for any service.

If you’re working with a startup, respect your potential users and let them give you their email addresses. If you’re trying out a new service, don’t fall for the viral invite tactic by helping these companies spam your friends. Enough’s enough.