Some people just don't know when to quit.

Today, struggling Blackberry maker Research In Motion (Nasdaq: RIMM) announced its new BBM Music service for social music sharing. Here's the rundown. For $5 per month you get to select 50 songs tied to your personal profile and can swap out up to 25 songs each month. The twist is that you grow your music collection by being able to listen to songs your friends and other members in your BBM Music Community have picked.

The more BBM friends you have, the more your library will grow. The service will rely heavily on trying to build out network effects, since clearly your $5 will go a lot longer if you have more BBM friends. The company has an installed base of 45 million BBM users to pitch to sign up.

RIM's declining market share won't help its attempts to promote network effects. According to Gartner, the Canadian company's market share fell to 11.7% in the second quarter, compared to 18.7% last year as Google's (Nasdaq: GOOG) Android and Apple's (Nasdaq: AAPL) iOS grew their shares.

The 50 song limit is insultingly inadequate for $5 per month. What you're paying for is the novel approach at sharing. No one in their right mind would pay that much for just 50 songs. The company has a tough sell trying to lure users away from popular services such as Spotify and Pandora (NYSE: P).

Spotify's social sharing implementation is pretty hard to compete with: It connects with Facebook to find your friends and allows you to publish public playlists for all to enjoy. You can even send songs directly to your friends. Spotify is pricier at $10 per month, but even the free service is pretty compelling.

BBM Music really has nothing going for it. Its laughable song limit makes it useless compared to other cloud music locker services from Google and Amazon.com (Nasdaq: AMZN). Its attempt at social sharing, while unique, is trying to build network effects from the ground up instead of simply plugging into the existing network effects Facebook enjoys.

I'll go as far as to make a prediction: One year from today, BBM Music will be gone, dismissed as a failed experiment, while Research In Motion's market share drops into single-digit territory.