Back off

Are back buttons on a website bad? It's a question and request that almost always comes up. My feeling is that back buttons signal a flawed navigation model, but is that correct to assume? So let's argue that back buttons are for error correction - the user didn't want to follow the route they'd chosen. Should the browsers back button not be for this purpose, but then ok, checkouts and other transactional processes can fail when users resort to the browsers back buttons, but then the back buttons is obsolete here, the buttons should be user centered and be inteligent to direct error correction - 'Edit your details' rather then the meaningless 'Back'.

And on less transactional sites? 'Back' has to show a flawed navigation model, i can't think of a reason why it woudln't. The users journeys should be informed and logical and the site should guide.

Please any ideas?