A feature substantially less useful than the ability to copy and paste, instead WP7 sneaks in a “copy and search” function. While in Internet Explorer, you can tap on a word to highlight it, and if you then hit the search button, a Bing search will be performed on the word. Useful if you need to look something up I suppose.
So they already have a method of highlighting text, and copying it into another program. Why isn’t copy and paste built-in again?