Fresh content is a very important asset for the growth and popularity of your site. There are many reasons why this is important.
First and foremost, having fresh content benefits your link juice. The more you write, the more opportunity you have to be linked to. I wouldn’t say to take the Twitter approach, however. When writing an article, write something of substance. Write something longer than that — but not too long so as not to neglect your readers. If your content actually requires great length, break it up into small pieces and link to each other in subsequent articles, making sure you link appropriately to refer them to a previous related article. Create a series of related posts. This works in blogging as well. Michael Gray recently did a series on local search. If you have not seen his vast interview coverage, I urge you to check it out to get an idea of how he did it.
Fresh content also gives you crawling visibility. Search engines will completely neglect you if they see a website that hasn’t been touched in ages. Having content updated regularly means that you’ll have the spiders visiting you more often, and that gets your content on the search engines up sooner than a site that doesn’t update as often. If you just update an image, the spiders might come back. Content does matter.
If you write for a very specific vertical, it is important to have the content written by you, the expert, rather than someone else. Ultimately, you are the closest person to the service you provide or the product that you sell. You would be doing yourself a great disservice if you shifted that responsibility to someone less knowledgeable. Furthermore, as I learned in the Eric Ward linkbuilding webcast:
There is no outside party that has the passion to help you as much as you want to help yourself.
With more carefully crafted content, you get more link juice, and this in turn results in more visibility in the search engines. When people search, they are actively looking for someone to fulfill a basic need. If you fulfill that need, you’ve won.