[eluser]skunkbad[/eluser]
If you enabled short tags there is a risk of a conflict when using xml files in your application, which I do. Xml files have a document declaration (if that's what you call it) that is wrapped in what looks like short tags. I have views that are xml templates. I can pass data to those views, and then send them with xml headers. If I enable short tags, php will output a fatal error.
Short tags are also a bad habit to get into using. I can't tell you how many scripts I have had to update to standard php tags because they don't work on my server with default configuration.
The beauty of php is that you can do things in many ways, but over time you will understand that short tags are bad, like smoking cigarettes, or like playing around with a prostitute.