Date in URLs

Hi,

I have noticed that several blogwares uses dates in their permalnks' 
URLs.
I believe this is a serious mistake because a document can be updated 
and thus its date is modified.
It's even more a mistake since time-stamp management are built-in 
features in most blogwares.

So I'm wondering if the notion of time can be applied to URLs or if 
it's only a matter of location.
Do you think I can write an article about that without being ridiculous 
?