In previous versions of iOS, it was not possible to upload files through Safari, given it’s lack of a filesystem. If you have browsed our forums or other website that allows for file uploads, there is no current way to access a file to share from your iPhone. The most common use might be attaching a photo for upload, which isn’t possible. The choose file is not accessible in iOS 5 and previous versions. The workaround for many sites, our site included, is to offer an iOS app with that functionality built-in. This has been changed with the current iOS 6 beta release.
As noted by fellow XenForo user Dinh Thanh, iOS 6 now allows for uploading photos or videos from within Safari. Devoid of a filesystem or Files app, the choice is either to take a new photo or video, or select one from ‘Camera Roll’.
It doesn’t appear as if Apple is too keen on adding access to any sort of filesystem, but this is certainly an improvement over the current state of sharing photos using an iOS device, which requires the use of an app.