I have been listening to discussions about Twitter and feel the time has come for me to chime in.
If you use Twitter correctly it is a fantastic tool for directing people to your online properties. Assuming of course there is some reason for people to visit your site. Don't think you can repeatedly post links to your shopping cart and people will go there and buy your product. That's not a good use of Twitter.
If you use Flickr and regularly post new photographs, that is something people will likely enjoy visiting. If you publish a daily blog (like this one) Twitter is an effective a tool for directing people to your latest post.
The key to using Twitter correctly is to be certain you have fresh content for your Followers to visit.
Twitter is a megaphone (or sideshow barker) that lets people know what is new and different for them to see. If they go inside the tent (because I like the sideshow barker analogy) and see the same thing they saw yesterday, they are unlikely to return.
Remember, Twitter is a social media marketing tool and social media marketing is all about building relationships, not selling products. Selling products comes under the heading of "Conversion" and conversion happens only after relationships have been carefully cultivated.
If you sell insurance it is possible you might be able to turn your friends into paying clients, but that doesn't mean you should be passing out business cards every time you get together at a neighborhood barbecue.
Relationships are precious. Long term relationships are even more precious and only come with repeated trust-falls. If you drop the person who trusts you to catch them, either by directing them to a scam, promotional web site or shopping cart, don't expect them to trust you again.
So in essence, if all you do is affiliate marketing and try to use Twitter to grow your network, don't expect to see good results. In fact, your efforts will actually work against you, likely causing your Follower count to decline.
I have had excellent results using Twitter to promote my online content, but then again I think I am using it correctly. Before you fault the tool (Twitter) take a good long look at how you are using it. The problem may not be Twitter, but what you are trying to do with it.