component GUID

I've read the
http://robmensching.com/blog/posts/2...nent-Rules-101 blogpost
which is very enlightning.

However, I still have some questions:

What is the scope of a component GUID? How does all this relate when using
mergemodules in different installers?

Lets say I have two different installers, installing to different folders
and both using the same mergemodule. The components in the mergemodule have a
certain GUID but they get installed in those different folders.

What if I uninstall the second installed application? What is the effect on
the first application?

I tried this scenario and the files in the first installed application still
exist after uinstalling the second installed application (somewhat expected),
but do get removed upon uninstalling the first installed application, which I
didn't expect: after all the component data got updated by the second
installer which is allready uninstalled.

Can someone clarify this please?