Relevance: all Social Media channels
Reframe your thinking.
Other bloggers, Tweeters, and colleagues in your industry are not necessarily competitors for your space on the web. Social Media functions on reciprocity. These people are potential partners in spreading your message.
This is a lesson that companies that contract with the Federal Government have learned. Yes, a contract might be fulfilled by LockheedMartin, but very seldom does anyone on the outside see the companies subcontracted by the contract holder. There may be two, or even dozens, of other concerns assisting LockheedMartin in fulfilling their contractual responsibilities.
How does this apply to Social Media? Simple, if someone produces content that is valuable to you, re-tweet it, or offer links to it on your other updates. Better yet, blog a response to it after you have shared the original material, and then share your blog entry on the same channels. Even better than that, if the original post allows for comments, make a useful comment back to the original poster.
By using their content to boost your message, you boost them in turn. Because you have responded to the original content, in one way or another, it raises your relevance, and enhances your appearance as a good Social Media “neighbor”.