Just to clear a few things up regarding ACARS
It is normally sent over VHF - but can be sent via SATCOM.
ACARS over HF is far from dead! but has opened up new routes to some carriers as they are now able to maintain contact with flight ops in areas of the pole where there is no sat coverage.
The ACARS messages on the internet have not been decrypted merely decoded into a format that can be read by the enthusiast and not just the airlines software.
However the scanning of ACARS is likely to die out soon as ARINC have released a version of the software that will encrypt all of the information end - to end.
As of yet I'm not aware of any airlines that use this upgraded ACARS - if you go to the ARINC website you will find the information about why and how they are encrypting it.
PS. it is using digital encryption so no chance of the anoraks / other airlines having access to it in the future!
PT6A