Twitter has some great marketing potential, hence why everyone is starting to get on the bang wagon. Unfortunately the "follow bots" are appearing and I would suggest you simple don't just refollow anyone that follows you but look at their contributions and index scores...ie. following 25k and 2 followers will represent no value.
Treat it like a conversation you would in real life, use it to develop a branding of yourself and our business not simply a post after post of blog links and it will return dividends. I am seeing some great results in terms of traffic and my twitter stats are only low....take a look at
Twitter / MikeRalph