So, I've noticed a trend; people suck at knowing when to use backslashes versus the plain ol' slash. Here's a quick and dirty answer: IF YOU AREN'T A PROGRAMMER THERE IS NEVER A GOOD TIME TO USE A BACKSLASH! Here's why.
The backslash (\) has a relatively short history, but in that short amount of time people seem to have been brainwashed into using it for all kinds of things.
If you're a programmer, you appreciate the backslash character because it lets you write somewhat complicated non-printable characters by "escap-ing" them out. For example, "\n" means "print a new line" in quite a few modern languages.
When Micro$oft bought/stole CPM and turned it into DOS, they inherited the use of the backslash as a directory separator (i.e. "C:\DOS"). Why? Because at the time it used the slash ("/" or, "forward slash" which I cringe at when people say) to specify options to programs (i.e. "fdisk /MBR") unlike unix which uses the "-" to specify options (i.e. "ls -l" ... much nicer IMNSHO).
Now, ever since the Windows 2000 era (which is rumoured to have had some linux people worked on it) you can use the unix-like "/" for directory separation (i.e: "cd WINDOWS/SYSTEM32/DRIVERS" ... try it!). So, the only thing left in the universe that non-programmers should see the backslash in would be command-line options to windows programs. So, since most newbies don't even know there is a command line in windows, THERE IS NO REASON FOR THEM TO USE IT!
By now, you might be asking, "So what?" or "Who cares?" or "What's the big deal?"
I've seen ads on TV and in magazines with web addresses that look like: "http:\\some-stupid-company.com\" and I've also seen LOTS of signs with things like "1\2 price" or "1\4 lb" STUPID! (I wish I had pictures, but I don't). I also really hate it when people say backslash when they mean slash.
So, unless you're a programmer, just forget about that "\|" key... 'cuz you aren't going to need the "pipe" character either.