Are all the Magnet minifigs now glued on and how should I remove them?
All new magnet sets introduced by LEGO will have the figures glued, as will any re-makes of existing sets.

History

In 2009 LEGO started producing sets of minifigures standing on magnetic bricks. At that time, the figures were removable, although some felt that they were of lower quality than the figs in regular LEGO sets.

In early 2011, however, LEGO started to produce Star Wars magnet sets where the minifigures were glued to the magnet. The problem was that LEGO Star Wars magnet sets violated a licensing agreement which said that LEGO could produce sets that contained Star Wars characters, but that they couldn't produce stand-alone figures. Apparently, one of the other big-name toy brands who was licences to produce stand-alone figures objected to the LEGO magnet products because they felt that the availability of LEGO Star Wars figures on magnets harmed their own sales figures. LEGO recognised that fans would be unhappy, but felt that it was in everyone's best interests to comply with requests to change their products.

To promote "a consistent consumer experience", all new LEGO minifigure magnet sets have had the minifigures permanently fixed on the magnet since that time, including the Pharaoh’s Quest sets launched the previous December.

This means that:


All sets that are new since January 2011 are glued.
Some sets that existed before January 2011 come in two versions - a glued version and a non-glued version. Confusingly, the sets have the same number and have been sold from LEGO shops simultaneously, and have similar packaging. Glued sets do have a note on the back saying that they are glued (in rather small print).
Any re-releases will be glued.
It might still be possible to buy non-glued sets. In December 2011 I was still able to buy certain non-glued sets from the online LEGO store in the UK. I assume that they were old stock.
Some parts are never glued - typically accessories like light sabres.


Some details for specific sets are available on TheBrickBlogger.com.

Incidentally, it is widely believed that one of the reasons that LEGO introduced the "Battle Packs" is to provide a way to buy minifigures that gets around the licensing issues.

Removing Minifigures

The most effective way to remove minifigures from the magnets is the "hot water process".

It turns out that LEGO does not actually "glue" the bricks, but uses a solvent that loosens the surface of the ABS plastic and allows the molecules to combine. The solvents are water soluble at certain temperatures, so hot water can weaken the seal between the bricks. Care must be taken not to overheat the water, however, as the melting point of ABS plastic is somewhat below boiling point.

Although the removal process does no damage to the LEGO, the places where the bricks were fused won't be smooth due to the fusion process itself.

Again, more details are to be found at TheBrickBlogger.com.

Disclaimer: I have not tried this myself.

Obtaining Minifigures

All this leaves us with several options for obtaining the minifigures we want:


Buy the sets that contain them (or figures that others have removed these sets). Battle packs and (for Star Wars) Advent Calendars are a good place to start.
Obtain old magnet sets that are not glued
Accept the rough edges left by the hot water method
Use parts from a combination of the above.


Response

The other thing we need to decide is how we respond to this change. My suggestions are:


Be happy that some sets were produced unglued.
Encourage LEGO to produce more battle packs by buying existing ones.
STOP buying the glued sets, and make LEGO aware that we don't like them.
Lobby LEGO to produce unglued magnet sets where licence restrictions don't exist.
Encourage LEGO to make statements about gluing more prominent on the glued sets.