Jakob Nielsen reckons that it's ok to use the passive voice when writing headlines for the web. In fact he thinks in some cases it actually improves the chances of you getting your message across.
Simple sentence structure, active voice, and positive statements have been key Web-writing guidelines for more than a decade. I don't want you to abandon these good ideas. They do improve content usability in most cases, particularly for body text.
However, recent findings from our eyetracking research emphasized the overwhelming importance of getting the first 2 words right, since that's often all users see when they scan Web pages. Given this, we have to bend the writing guidelines a bit, especially for elements that users fixate on when they scan — that is, headlines, subheads, summaries, captions, hypertext links, and bulleted lists.
That's what I love about the web. Bending the 'rules' (which are only really conventions anway). Complexity. Context.