Every now again I come across something simple, yet profound. The most-recent is on Grady Booch's blog at http://www.handbookofsoftwarearchitecture.com/:
"EA attends to the architecture of a business that uses technology. TA attends to the architecture of the software-intensive systems that support the business".
This simple statement embraces several messages (such as the linkage of business and IT), but one, in particular, is worth emphasizing: "EA attends to the architecture of a business". This is a great one-liner that really crystallises the emphasis of EA as opposed to TA, especially given that enterprise architects and software architects each deal with applications, technology and data. And, yet, their focus is quite different - one is a system, the other is a business.