One potential problem (and why I'm not posting my own collection here) is that it would enable installation of paid apps by people who didn't buy a license - piracy.
Regardless, is there some sort of archive to mitigate the above situation? Is there any effective way to do it without enabling pirating apps while respecting the rights of people who bought licenses?
I'd really like to see a XAP archive made available. I have a personal archive of some apps that I've bought. The idea is to mitigate situations where an app is no longer available on the marketplace (for whatever reason - temporary misidentification by MS certifier techs, trademark dispute, developers not renewing their store accounts, etc) even though you purchased it and have a license for it.