We offer instructions for upgrading your 2.x WordPress install via Subversion, so we certainly wouldn’t do anything silly between versions like deleting the entire directory that contains the ‘default’ theme, leaving your blog as a blank page with no indication of what’s gone wrong.
Oh, you found the ‘appearance’ tab in the admin backend? Ah, that’s my cue to notice that your website is broken, and instantly replace it with a nice picture of some trees. You like trees, don’t you? They’re very pretty, and I think sometimes you’ve got to put that above more practical concerns like not suddenly breaking everyone’s website.
What, you want your old theme back? Aww. OK, here it is in our themes repository. Oh, sure, I could just tell you where you can download it, but I have a better idea. Let me install it automatically for you instead! Just give me your FTP password, and everything will be juuuuust fine.
No, I don’t think there’s a plugin that will let you punch programmers in the face. Why do you ask?