Another factor that could come into play is "commentary" use vs. commercial use (somewhat as with Fair Use in copyright law). It's possible that the appearance of a photo of someone (who objects) on a blog or website that accepts automated advertising could raise more issues.
Photo (above): a visit to Mount Washington, NH; any such place is automatically "newsworthy".
Update: Jan 6, 2012
I found this mention on Wikipedia of "freedom of Panorama", protecting the right to photograph "architecturally original" buildings built after 1990 without infringement, link. It does not protect photography of individual art items, which may be infringing. Many museums prohibit indoor photography of protected items anyway.