It's not a security risk, it's a data loss risk.
Relying on one single backup strategy is what gets most people screwed.
Single point of failure.
That said, I can't blame them. The site was 100% run by hobbyists for fun. None of them were professional server administrators...
Avsim had thousands of custom user-made aircraft, repaints, and other addons for the ms flight simulator series. Only ONE such addon takes the typical user MONTHS of work. This is 13 years of user contributed HARD work down the drain. The loss of work here is very tragic to say the least...
Personally I would have never felt comfortable just relying on server to server backups, when 13 years of user contributed work is at stake. However, not being professional admins, they probably thought their server-to-server backup system was pretty clever.
Server-to-server backup is a good layer to have in a backup system. But it shouldn't be the only one. Not if you have that much at stake...
That said, unfortunately, even with multiple redundant strategies in place, something can and will always go wrong, that you haven't thought of before.
In their defense, backing up such a huge set of data is not that easy. You can't just go download 13 years of flightsim mod development. One simple plane model with textures, effects, etc... can go upto 40MB or more... I can't even begin to imagine the amount of data they had on there... I don't know if it was dedicated or colocated servers, but it seems to me that the only way to do this in full (non/incremental) without killing your bandwidth or waiting for the transfer to finish into eternity is by
sneakernet, and if it was a dedicated server, they wouldn't have had access to the datacenter to make a copy of the hard drive(s). The difficulties in making a full backup of such vast amounts of data is probably what made them put it off...
