Unfortunately, GOG"s introduction of regional banning/censorship has broken MaGog's harvesting of regional pricing information.
Until fixed, MaGog is unable to obtain regional pricing information on new games or identify regional pricing changes in old games.
Since I am on holiday from tomorrow until Monday, I will begin looking into it only on Tuesday.

Is it possible to compare my games (if I copy&paste the list from GOG) to the list I keep in MaGog? I've had a few occasions where I thought games where missing from my shelf but I can not check a few hundred entries every time by hand.

Not at the moment, I'm afraid. Not easily, at any rate.

I will add it to my todo list, but it may take a while because with the recent introduction of regional banning on GOG I have quite a bit of work to do fixing existing code before I can add new one.

ANNOUNCEMENT:
Version 4.2.0 has been released with the following features:

* Added optional display of the German game title (currently available for 37 games), as well as filtering by its presence or absence
* Added "Mac OS X 10.9.5 or newer" to the list of searchable operating systems

I looked at it a bit and I'm afraid it's just too much work for the worth of this feature.

Here is a simple solution to achieve the same end effect:
(1) Copy-paste your library (in list mode) into a text file (ctrl-A, ctrl-C, ctrl-V) at a point when nothing is missing and keep it in a safe place.
(2) When you suspect foul play, repeat into a new file and compare the two files using a text comparison application (I use Beyond Compare, but there are free alternatives, such as diff or comp).

Thanks for your time though (since it wasn't a "real" feature request). I'll keep that solution in mind. :)

An Excel file with formulas is quite useful too.

ANNOUNCEMENT:
Version 4.2.1 has been released with the following features:

* Added the option to differentiate between multilingual and monolingual installers when filtering by "downloadable file type" [indirectly suggested by JimRaynor.925]

Thank you for further enhancing MaGOG. Are these really the same installers? If I remember correct, GOG switched from one English installer for multilingual games to one installer per language (independent if one or more languages of the game were going to be installed). Is there any way to check if a game has one or more installers in GOG's library view? E.g. GOG lets me choose an installer language for Deadly Premonition, MaGOG says it's always the same installer.

Yes, when MaGog lists an installer as multilingual (i.e. lists more than one language, separated with '+', e.g. "Windows installer, English+Russian+French+German+Italian+Spanish"), there is really only one installer file for all the languages listed.

If there are separate installers per language they are listed separately by MaGog (e.g. "Windows installer, English" and "Windows installer, German").

As far as I know, there is no way of knowing this from GOG's library display, short of attempting to download the different language installers and seeing they are really the same file (again and again).

That's what MaGog is for, to assist where GOG cannot.

What will happen to Magog now with the unbundling? O_o

*explosion*

What's "unbundling"?

Thanks, will now always check when downloading multi-language games.

Thanks for the heads up.

Actually, it's not too bad. MaGog already has a mechanism for rebundling unbundled games back into one entry (needed for Cognition, Dracula, 4+5, X-Wing, TIE Fighter, etc.). So MaGog will remain with the current scheme of recombining all unbundled games into one entry.

Obviously, I have no way of preparing ahead of time for this, so every time a game is unbundled, it'll break the "downloaded files" info and "Get From GOG" feature, then I'll add the new rebundling data and everything will return to normal.

Expect some mayhem in the upcoming weeks, but no explosion.