Lion is not available on optical media, meaning you cannot purchase a DVD disc to boot from if you need to repair or reinstall Lion. You can however burn your own bootable Lion disc using the trick mentioned above.
According to recent Apple press release, a Lion installer will be made available on a bootable USB thumb drive through the Apple Store in late August.
The direction Apple is now taking to replace bootable Lion media involves creating a small 650MB partition on your boot drive, to store a hidden volume called Recovery HD. You can boot from this volume by holding down command-R at startup (or the option key, followed by selecting Recovery HD), and it can be used to repair or reinstall Lion. This concept is very similar to booting from a pre-Mac OS X 10.7 install disc, however the Lion Recovery HD also allows you to browse the web using Safari.