How do I ask contacts to update their contact information?

How do I ask contacts to update their contact information?

I'm hoping there must be an automated method to ask contacts to update their own contact details. Is this possible? If so, please advise how to do this in CRM. And if there is no automated method, is it possible to create a custom email template to show contacts their current data and ask them to perhaps fill in a webform with any changes?

Plaxo and SalesForce.com have this feature. In SalesForce.com, the user clicks on "Request Update" and this sends an email to the contact with the contact's current information. The email asks the contact to check the data and click on a link to a webform if there are any changes required. The contact details and webform should be customisable to include custom contact fields.

Forgive me if this has already been asked, it seems such an obviously essential feature but I cannot find it in CRM. Thanks for your help.