I just followed your link to the Crashplan help doc and you're right, their syntax is messed up for Net Use. I think there's some typos in their examples.

I see that you're trying to map a DRIVE LETTER to a share. If you want to do that, then you really do need the SHARE NAME in the net use command. Think of it like this.

The share name represents a folder on that server. If the server has more than one share you can get a list of the shares, but a list of the shares is not the same thing as the server's root directory. For example the server might have folders like this:

Photos
Program Files
Documents
bin
etc
Windows
shell
Videos

With the bold items being the folders that you have shared. But the thing is, looking at a list of those shares is not the same thing as going to that computer's root directory. In fact, those share's don't even have to be in the root at all. Maybe they have a folder that's six levels deep and they only shared a subfolder of that folder. Whereas somewhere else they shared something at the top level.

In any case, for users connecting to the server, you only want them to access the SHARES, not all the folders in the root. So by default, if you browse to the server name, you can see a list of its shares, but you cannot map THAT VIEW to a drive letter. It wouldn't make sense to do that because you would be unable to save files to its root directory... there IS no root directory.

Once you're down to the level of one of the SHARES then yes, you can make that the root directory of a mapped drive and that will work.

Is that helping to make it clear why NET USE doesn't work without a share name after the computer name?