Actually they compress quite alot a game like this could be 80Gb's uncompressed, alot of this is the sound... With Blu-Ray developers can keep the sound at an ultra high standard, its the whole uncompressed vs mp3 debate all over again, anyone with ears will appreciate high definition sound, the PS3 with Blu-Ray is the only next generation console with the storage capacity to fit uncompressed HD sound, it can also leave textures to a level of uncompression we have never seen before, its nothing to do with showing off it is common sense, if you have the space you use it, until now developers have only had 8.5Gb's to mess with, Blu-Ray is like telling a kid he can buy everything he wants from the candy store, the kid will take advantage of the privelage and so do developers... And as Tallteen nicely stated compression reduces the quality, and as the PS3 exclusives are showing this level of uncompression is already showing results none of the competitors can match in the sound and graphics department...

I doubt it is going to cache 22 gigs on to your hard drive haha...the information on the disk is the 22 gigs...for all we know it wont even cache anything on the system itself