An Email I wrote to one of my developers. Thought I would share.
So, lets just bring it down to one scenario.
I have a People's table and a Building's table. One table has a various amount of people including names, DOB and various other small tidbits about their life. The building has the same. Its name, its type, and address and various other tidbits.
Now, lets say I have an Images Table. I want to link images to the buildings and to the people. But all people and buildings have more than one image. Instead of adding a new column in that image table to describe the type of image it is for (also adding another table to describe the types of images). I just have one relation and that is a Item_Id. That image table is then queried when ever buildings or people are queried. Only searching for the people Guid or the Building Guid.
Now, lets say I have the images table again, but the people table and buildings table have INT's as their identifier. If I pull from the Images table all images that have an Item_Id == 5, I could get both personal pictures and building pictures. Including any other type of picture I take. And thats why I don't like to use INT's unless I am positively sure it won't cause adverse affects later on.