Not 100% sure I get what you mean - but if you just need a guest book (or any block) on each page of a certain type (e.g. a profile page), you are best off adding the block in the 'page type defaults'.

Page types:
http://www.concrete5.org/documentation/using-concrete5/dashboard/pa...

Page types defaults:
http://www.concrete5.org/documentation/using-concrete5/dashboard/pa...

Note the bit about 'Set up on Child Pages'. This functionality allows you to add a block once to every page that uses a specific template/design. Each page of that type will then have a new instance of the block, but that operates on it's own. As soon as it is edited, or used it is unique to that page.

There is a block called 'guestbook/comments' that comes as standard with Concrete5, and also a great extension add-on for this available in the marketplace:
http://www.concrete5.org/marketplace/addons/advanced-comments/...

Hope that answers your question. If not, just provide more details here.

Unfortunately, there are no "page type defaults" for the profile pages. It's a matter of editing your profile and the layout inherits to all other users' profile pages. So, unless the block you're adding to the profile page is coded to know which user the page belongs to, you will see the exact same content on every profile page.

I know I responded to another thread about Concrete Wall and Sharing Box. Both of these blocks will display based upon the user!! Another block in the marketplace that is responsive to each individual page is the Disqus add-on.

If using a facebook comment box would be acceptable, you could always get the code from facebook and then use Magic Data, and my how-to, to have a different comments thread on each users wall!!

Magic data:
http://www.concrete5.org/marketplace/addons/magic-data/...

how-to:
http://www.concrete5.org/documentation/how-tos/designers/integrate-...

Whoops - yep - apologies, I didn't take on board that this was talking about the standard user profile pages!