The package manager does not show a dialog window that lists the packages that will be installed and removed before actually installing packages; at least if any packages are implicitly selected (or deselected?). Most people won't check the Installation Summary view before starting the install, and so they won't notice unexpected side effects. (This view has a few problems as well; see 157313).

I ran into this when having kernel-default installed and selecting novfs-kmp-smp, and expected the resolver to ask me whether I was sure I wanted to install kernel-smp, which novfs-kmp-smp depends on -- and was surprised that the package manager just proceeded. (The kernel-default and kernel-smp packages don't conflict.)