My instinct is with yours, but in some very simple use cases, it can make sense. For example, you've got a legacy PHP web application you have to maintain, and

My instinct is with yours, but in some very simple use cases, it can make sense. For example, you've got a legacy PHP web application you have to maintain, and it's got spaghetti code all over the place, but all uploaded user content is stored / served from a single directory. You can probably use an S3-backed file system to replace that directory. Obviously if you try to do, say, an "ls -la" on that directory and there are a lot of files in there, you may be waiting a while, since that translates to a lot of API calls. Similarly if you have something like a virus scan running on the box, it's likely to be tripped up. But if you know the only thing using that directory is doing simple CRUD operations, it might be easier than trying to retrofit the application itself to talk to S3. Especially now that S3 has strong consistency.