This is why you need a blog...

...a few weeks ago one of my colleagues sent me an email which contained the details of a document I might need to refer to, the document could probably become a wiki but that is another story for another day.

This would be fine but the email also included the line "if you delete this email just search for the document using this search string"

...ermmm okay...but If I've deleted the email how will I (a) find your reminder and (b) know to search using a particular search string.

This seems to me to be one of the best reasons for having a blog instead of relying on finding/not deleting emails!