I believe that one of the signs of a good tester, is somebody who makes the job of software tester indispensable to their company, but does not make themselves indispensable.
Sharing information is key to a testers role. If you find yourself garnering information that is not being shared with others, you probably aren't being an effective tester. With a myriad of quick and easy ways to share information, from wikis and instant messengers, to e-mails and blogs, as well as good old talking to someone, you should have no excuse not to.
Remember as well, if you make yourself indispensable you limit your own chances of moving forward and learning new things because the company cannot afford to have you do anything else. That is not my idea of career satisfaction, but YMMV.