Seeteufel writes "Microsoft's failure to comply with an antitrust settlement about browser choice has severe consequences. The European Commissioner for Competition Almunia set a fine of €561 million (~$732 million) for the unprecedented break of agreement. Microsoft admitted its mistakes and offered further concessions."
A pretty costly bug it seems. From the EC press release: "This is the first time that the Commission has had to fine a company for non-compliance with a commitments decision. In the calculation of the fine the Commission took into account the gravity and duration of the infringement, the need to ensure a deterrent effect of the fine and, as a mitigating circumstance, the fact that Microsoft has cooperated with the Commission and provided information which helped the Commission to investigate the matter efficiently."