When I was in consulting doing software integration work, few things infuriated me more than client "bug reports" arriving in the form of an email containing a 15 megabyte MS Word doc with a bunch of un-annotated screenshots.
I really hope Google someday opens up the awesome bug report/screencap feature in Google+, that lets you highlight part of the screen and redact sensitive parts.
In OSX, the cmd-shift-4 (and 3) keystroke which screenshots right in to a file are near life-transforming. Snap, drag the file into an email, and it's done. I'm sure there are utilities in Windows which do this, but having it built in is great - no apps to start or install.
That said, from a geek standpoint, I still prefer having the raw image file that I snapped in a folder someplace so I can refer to it later without having to go through sent emails, but that's just a personal preference.