Add activity when contact is created

This has been prompted by http://civicrm.stackexchange.com/questions/4372 which reminded me of other posts on the forum or SE where people have wanted to be able to identify all contacts who were created in Civi on, before or after a certain date.

I plan to create a new activity type called " Created on". It would be system generated when a new contact was created in CiviCRM. Originally I had thought the activity would only include the created date, but based on http://civicrm.stackexchange.com/questions/4792/how-to-check-who-creates-a-certain-contact I can see that including the person who created the contact might also be useful. This would let people easily search on both those things.

I was toying with the idea of seeing if I could retrospectively create activities for all contact where that information is stored in the civicrm_contact table, but then the retrospective activities would not include the person who created the contact if that was included in the activity_type. I know that information is in the log tables, but I think extracting that would be way above my skill level.