You can bid on trademarked terms but your ads won't show. You can bid on trademarked terms only in the USA. Otherwise you'll get this note:
That's not a trademark issue, that's copyright. No, those are actually "i"s... You're only forbidden from using TMs that advertisers have submitted paperwork to Google for. All TMs are not automatically protected.
Here's a great summary of TM issues: http://searchengineland.com/070903-150021.php And a very current post: http://searchengineland.com/080324-090813.php