e-mail strangeness

I want to begin by stating that I do send "informal" e-mails to friends and family. Let me explain my definition of "informal" -- perhaps an example is best:

Hey - wanna grab coffee today. Lemme know

or

did the package arrive?

I do start group e-mails to my friends with a 'Hi all" - just so they know it is to MANY people (god forbid people reply all and say something horrible by accident).

I try very hard to follow this example (except with the husband):

Dear (or some kind of greeting) Name,

Content content Content

All the best,
my name


BUT - I always thought a formal e-mail should be written like a letter. A formal e-mail is one to someone you have never met, a boss, a potential business contact or a professional acquaintance. It is the e-mail you send to a business.. etc

I have been inundated by e-mail from students who want to Crash my class. many of them cannot be bothered to address the e-mail to me.
Just a 'Hey I want to take your class but it's full. Can you give me a permission code."
No salutation or greeting and in some cases not even a closing or signature.
Just an order.

They were able to track down my e-mail, they couldn't address the letter to me?

And these are people who WANT something from me. And most of these are college SENIORS who will be graduating in just a few short months. Can you imagine if they send an e-mail like that to a potential employer?

When did we loose civility? Are we not teaching etiquette anymore?

But since this is world where some people think it is appropriate to mention their vaginal cyst in their Facebook status (really this happened) - I guess I shouldn't be surprised.