Do you have more than one Facebook profile? You may have a personal profile and also manage the page for a small business or brand name.
For example, many people own small businesses that use Facebook as a marketing tool. You may want to add a comment as yourself, not as the official voice of your organization. Or you may just want to avoid having your business "like" all of its own posts.
Here's how to leave a comment (or like) on your organization's page as yourself:
1. Log into Facebook as usual.
2. Click the drop down arrow to the right of Home.
3. Click on your company's profile.
4. Click Edit Page and Manage Notifications.
5. Under Posting Preferences, uncheck the box that says, "Always comment and post on your page as [Company Name], even when posting as [your name].
6. That's it!
Edit, July 5, 2012: Facebook has added a new voice feature to help with this issue.