The service called tinyurl.com for mapping short urls to long urls has some parallels to ENUM for mapping short-numeric-strings to longer uris. Some of the problems tinyurl.com may have had to solve may have application to ENUM and SIP.
Say you know someone with a longish SIP URI that you want to call using a phone with only a numeric keypad (e.g. sip:email@example.com). Say you had a web page you could use to create a numeric ‘short-cut’ for the URI. The web service creates a ‘reusable’ ENUM record similar to how tinyurl creates a ‘reusable’ url. Then you call your friend at that temporary ENUM number.