I don’t actually read superhero comics, but Eric over at Websnark made a really good post about retconning– changing the continuity in comics– that’s a really interesting look at a popular device in fiction in general.
That phrase, by the by, which is a lie. Retconning doesn’t change ‘what they thought they knew.’ Retconning intentionally takes what they knew and made it wrong. It is a contradiction of your fans’ expectations and a complete alteration of the context your stories are told in.
It is a tool, in other words, but it is one that should be used very, very, very rarely, because it deliberately breaks the emotional investment your fans have in your core product: your story. You take a significant risk that your fans will not then reinvest every time you do it. Which means you’ll lose some of your fans every time you do it.
The biggest retcon I’ve seen in any of the webcomics I read is in The Midlands, which did a total reboot recently. I’m not sure if I like it, but given the direction the author thought the comic was going– IE nowhere, but with more magical artifacts– I can see why she did it.