Imagine this case, like a customer of mine had: You have all kinds of project sites for all the projects in your company. Of course you have a site on top that links to all these sites, shows you some additional info etc..
Now, my client wanted to manage all issues on the top level site, while all tasks (multiple tasks for each issue) are on the project sites.
Custom development, was my first idea..until a colleague came with a brilliant idea:
“You can create a site column on the top site (type=lookup to the issue list), and reuse it on the project sites. That way you can do it ootb!”
Good to hear that some people actually think through the MOSS Matrix! I guess he took the red pill instead of the blue one 😉