Opening a .mobileconfig file in Lion exposes an otherwise hidden System Preference, 'Profiles' as shown here.
The .mobilconfig files are typically used to manage network settings on iOS, including the Access Point Name (APN).
To view this in Lion, just open a .mobileconfig file from Finder and System Preferences will now reveal 'Profiles' with a means to manage multiple profiles.
If you install a .mobileconfig, Profiles will remain available in System Preferences; if you delete all profiles, then Profiles no longer appears in System Preferences.
This doesn't yet seem to affect network access or browsing at all, so it is possible this feature exists to pave the way for more unified management of APN on desktops with mobile internet access, similar to iOS. You saw it here it first!
[crarko adds: I think the point of this is to indicate possible future support of cell networks in OS X, perhaps on a future MacBook Air. It doesn't seem to have any immediate utility.]
Mac OS X Hints