I think I'll point to this as one of the examples of how AWS has been scrappy and successful. (Yes, I'll get like 10 flames on this comment.) They made this nice simple API for S3 that has become a de facto standard. They added lots of features and security controls, and I can easily imagine an architect saying "everyone should just adopt S3, it's so easy!" But huge, paying customers were used to tape libraries so they said, damnit, fine we'll pretend to be a tape library even though that is super weird on some level... Meeting users where they are can be a superpower.
As always the problem seems to be the 'Hotel California' issue: you can check out but you can never leave. Once you have massive data in AWS there is no efficient and affordable solution to move that data back out; you are locked in forever subject to whatever future terms Amazon may chose to impose.
Dumb question, and I'm guessing this is a "if you don't know it's not for you" situation, but what is the point of a virtual tape? Isn't the point of a tape that it's not virtual? Or is this more replicating tape software apis (WINE/proton style) so you can get rid of physical tapes (because you no longer care about their physicality) without having to change your backup strategy?
HEY! Before you adopt this check the bandwidth egress costs! Seriously.

Your disaster recovery plan will need to budget for extra egress costs if you ever need to restore something big from one of those virtual tapes. AWS charges for egress -- downbound -- bandwidth but they don't charge for ingress -- upbound -- bandwidth.

(And I think it's funny their icons and images look like old school DECTapes.)

My first and only experience with tape backups was in 2014 working with the BBB of Chicago. They were using tape backups, and there I learned that almost no company that small should be using tapes. Unless you have one or two people dedicated to handling that plus whatever other backup solutions you have in place, it won't end well.
> Tape Gateway stores virtual tapes in Amazon S3, Amazon S3 Glacier Flexible Retrieval, and Amazon S3 Glacier Deep Archive, protected by 99.999999999% of durability.

That’s a lot of 9s.

Anyone considering putting giant amounts of data into AWS or most other big clouds should be sure to do the numbers on retrieval. All the big clouds have "roach motel pricing" -- data is free or very cheap to put in, and expensive to get out. Outbound bandwidth costs from AWS are astronomical, so make sure you are not going to need to stream down all that data or move it any time soon or that you have compared that cost to your in-house solution.
Having to restore data from Mag Tapes over decades and getting CRC errors maybe 20% of the time, this cannot possibly be worse.
Tangent: What's the cheapest way to backup a few TB of personal data these days, pricing based on the premise that I probably will never need to retrieve it (due to local backups as well), but I don't want to pay thousands if I do have to (hundreds would be okay). Glacier Deep Archive?
AWS doing tapes like this feels weird to me. The physicality of the thing is kind of the point in my mind. Virtualizing the last line of defense seems wrong, but perhaps I could be convinced otherwise.

Why doesn't Iron Mountain or some other competitor offer a service like this?

It's been a long time since I've heard the word "tape" in my circles (I can't get John Cleese's Institute for Backup Trauma out of my head: https://www.youtube.com/watch?v=q_9wIupr9Hc).

That being said, kudos to Amazon for having a solution for those who aren't in my circles and still use them.

I think it's worth pointing out that this service was first released in 2012.
"Tape Gateway supports all leading backup applications"

Only huge companies like Amazon can be this dumb. They don't even mention tar or pax, the two most common tape backup applications.

Also, how will this magic Amazon "Tape Gateway" back up petabytes over slow links? There are many data heavy businesses that don't necessarily have tons of Internet bandwidth. Fully saturating a 100 Mbps outgoing connection will only get you 1 TB a day, so what happens when you have a tape's worth of new data daily and an already heavily used Internet connection?