In the documentation for pyvenv (https://docs.python.org/dev/library/venv.html), there is a table that shows by platform the command required to activate a virtual environment by OS.  For Windows, the values are:

Platform        Shell       Command to activate virtual environment
-------------------------------------------------------------------
Windows         cmd.exe     C:> <venv>/Scripts/activate.bat
  	        PowerShell  PS C:> <venv>/Scripts/Activate.ps1

The commands are incorrect-- they contain forward slashes and should be back slashes.

Forward slashes work fine in Windows, for both the command line and PowerShell. Windows always displays backslahes, but accepts either (as well as any combination of both) in paths.

Since windows users expect them to be backslahes, though, what's the motivation for using forward slashes instead?

I haven't tested everywhere but some versions of Windows don't in fact 
accept forward slashes on the cmd.exe command line. Suggest changing to 
backslashes as there's no reason to do otherwise.

All versions of cmd.exe want backslashes in paths for the commands implemented _by_ cmd.exe - those interpret a forward slash as indicating an option.  For example, here on Win10 Pro:

C:\WINDOWS\system32>dir c:\Windows\System32\xwreg.dll
 Volume in drive C is OS
 Volume Serial Number is 5E8B-CFAC

 Directory of c:\Windows\System32

10/30/2015  02:17 AM           120,320 xwreg.dll
               1 File(s)        120,320 bytes
               0 Dir(s)  2,880,244,813,824 bytes free

`dir` is implemented by cmd.exe, so that example doesn't work with forward slashes:

C:\WINDOWS\system32>dir c:/Windows/System32/xwreg.dll
Parameter format not correct - "Windows".

The key point here is that if I run the example as given on my Win 8.1 
box, it doesn't work. (The venv I'm using is called nw0).

d:\tim\.venvs>dir nw0\Scripts\activate.bat
  Volume in drive D is New Volume
  Volume Serial Number is 2639-22DA

  Directory of d:\tim\.venvs\nw0\Scripts

30/03/2016  07:45               547 activate.bat
                1 File(s)            547 bytes
                0 Dir(s)  458,354,536,448 bytes free

d:\tim\.venvs>
d:\tim\.venvs>nw0/Scripts/activate.bat
'nw0' is not recognized as an internal or external command,
operable program or batch file.

d:\tim\.venvs>

New changeset e6e35ff744fe by Senthil Kumaran in branch '3.5':
issue27045 - Use backslash in windows path to script file.
https://hg.python.org/cpython/rev/e6e35ff744fe

New changeset 2173063cbae8 by Senthil Kumaran in branch 'default':
merge from 3.5
https://hg.python.org/cpython/rev/2173063cbae8

This is fixed and online docs will reflect it when they get built in their next build cycle. 

Thanks for the report.