First, nice to see this finally escalated into like-minded people and constructive discussion...
Surely you mean titlekeys? getting the titleid is ridiculously easy for commercial DSiware - just backup it to SD and check the 4-letter folder name created under /private/dsi/ (for example if KAAV, convert KAAV from ascii characters to hex = 4B414156, then the titleid is 00030004-4B414156)
Even then, a titlekey can be ripped out of a ticket, which can be extracted from the nand of a console which owns the title (not saying they're not important!)
Again the real problem is not being able to download the titles themselves (if they're also removed from the CDN)
And (while that could probably be researched and simulated) the fact you can't uninstall/backup titles the official way without creating a shop account...!
We already have one (although it's illegal to share, and probably only works as-is on dev consoles) - TwlNMenu; however, apart from having to invent such a software, there are 2 big other problems:
1- access rights: despite what happened in practice, physical games can access sd/nand and viceversa but only if an appropriate bit is set. No big deal though if you have access to a digital game exploit
2- signatures: any ticket created with titleid+titlekey (or even a complete original ticket hacked to be installable on all consoles) would be unsigned, so while installable (as the DSi doesn't have an actual operating system preventing unauthorized things, the above mentioned access rights are done in hardware) they would be rejected by the home launcher...