Cooltechzone has said that Microsoft has bought out Opera. However, neither Opera nor Microsoft have anything on their website about it. According to the site, the other bidders was the search giant Google.
[Update via RSS] Slashdot quotes Opera PR as rumours being false - "If I was working for Microsoft I think I'd know it".
[ZDNet Update] Opera denies Microsoft takeover - "First it was Google, now its Microsoft?"