Actually, re-downloading isn't a problem if you make a backup or two. IMO the main risk with downloadable distribution (in terms of companies going out of business) is if there is online activation required to install or play the game. This could be fixed by having a patch created (and maintained if there are additional game patches) to remove the copy protection and held in case any authentication servers are shut down (for whatever reason) or some time limit passes and the game becomes old enough that there isn't enough revenue to justify needing copy protection.
Yes, being able to archive it can reduce the importance of being able to download again, but after a flood were I live having the ability to get the game again without having to re-purchase is a perk of digital media in my view. Some games (Divine Divinity) are worth buying again if need be but others do not get played enough to be worth in (it seems that Beyond Divinity will be that way from what I have seen so far). While tge importance of the provider staying around varies between customers, it is a factor to take consideration.
