Using the social networks such as Facebook & Twitter to promote your wares has become a very popular way to reach 1000's of "eyeballs" with 1 click of a button.
HOWEVER.... there is "etiquette" & ways to get potential customers to read your ads. Now this is based on MY surfing habits. I would think a lot of others feel the same.
Most of this is for both Twitter & Facebook (unless it says different)
First.... DON'T post 2 pages of "look at my stuff"... especially on a personal page. I will NEVER "listen" to anything you have to say & will probably "unfriend" or "unfollow" you in a heartbeat. DO.... spread out your posts or tweets with a product... then an info .... then a funny video ... THEN back to a product. If I find the info worth reading, then maybe I will find your product link worth clicking on too.
Second... DON'T hijack a fan page with your products on someone else's page, unless it is specifically for that as http://www.facebook.com/businessesgrowingtogether is. DO comment IF it is relevent to that post. Or simply hit the "Like" button.
Third ... DON'T spam. Both on Twitter or Facebook messages. A message every hr about "look at your stuff or join a group" on FB messages or posting the same tweet over & over may get you banned from both sites. At the very least, I will unfollow or unfriend you REALLY Fast! DO send a message on FB once a week or so.... & tweet different products at LEAST 20 to 30 min. apart.
Fourth & last.... DON'T connect your Twitter TO your FB page.... this will only result in Pages & pages on your wall & no one will even look if you actually have something important to say. DO connect your FB Fan page TO your twitter. This way, if you have a few things to post on your business fan page.... it will tweet as well without filling up page after page!
Using this information is totally up to you. It is only my opinion but, as I said in the beginning, it is based on MY reading habits.