Sony America has patented the wacky idea of degradable demos.
In other words, a nearly complete game that diminishes over time until you pay the full amount.
The patent (spotted by Siliconera) describes various ways degradation could manifest.
You might start with a big, powerful weapon, but this would shrink and weaken. Racing games may shed tracks after a number of plays and characters themselves will be marched up to the degradation scaffold.
Game visuals and sounds may be dampened, too.
Starting with a full game will require a bigger file, one presumably unwieldy for download. The upshot of this is that Sony can distribute these trials on-disc, and provide an unlock key to restore the degraded content.