That is the major problems with all forms of copy protection, be it with ebooks or music files you download off the internet. One hard drive failure (or even just the standard becoming obsolete) can render your entire collection near unusable.
If you could pay like £2-3 (a bit less than normal price) for a protected book, and normal price for an unprotected copy I would buy a lot more ebooks. As it is I am unwilling to invest in something that will not be readable in a couple of years. If the prices reflected the fact that you weren't cutting down trees to publish the book I'd be more willing to buy them too.
-=Trying to be useful=-
There is a BeOS eBook reader that supports those formats, don't see why there shouldn't be a converter/reader for other systems...
http://www.bebits.com/app/2618
Hehe Googling "EBXA Ebook reader" gives this thread as the first result. :)
Don't know if this is related, but seems to be a Sony ebook format, may have some relevant information:
http://www.sven.de/librie/Librie/BBeB
Or if you know someone who can program in C, and read japanese, here's a C-library for accessing EBG, EBXA files:
http://dir.filewatcher.com/d/NetBSD/...gz.287777.html