Comment 12 for bug 248268

I was just about to file the behaviour that was added here as bug.
I think Jeremy-list's suggestion on 2008-12-05 is very good and would suit both the needs of the original bug filer as well as ours, without the need for a pref.

Here's the use-case:
I am a developer. I want to install all packages needed to compile Foo, and I need to keep them. Manually installing them is too much hassle given the strange library package names in Debian, build-dep is really useful and an important criteria when choosing the distro.
This (me wanting to keep the deps) is the common case. OTOH, I occasionally have to compile a package from source that I just want to use. Esp. in cases like mplayer, it's nice to be able to easily remove the build deps again. In this case, having them all set to manually installed and removing them manually is just as hassle-some as having to install them manually. (That's probably where the original complaint here comes from.)

Thus, I think that tracking (for autoremove) the build-dep installs differently from the normal package installs, and allowing a "remove-dep Foo" (which only removes the build deps that are not needed by some other build-dep Bar that I also did), is the ideal.