You should be able to scan wirelessly too:

Built-in Wi-Fi technology allows you to easily print and scan wirelessly virtually anywhere around your house.

But you may need a special Canon software to do so, although it does not mention wireless explicitly.
Or maybe you can't scan wirelessly from the printer-scanner, only from the computers:

For network users, Auto Scan Mode is only available when scanning at a computer using MP Navigator EX software and selecting the 1-click feature then "save to PC".

Built-In Wireless: Print and scan wirelessly from any Wi-Fi enabled computer around the house.

http://www.usa.canon.com/cusa/support/consumer/printers_multifunction/pixma_mg_series/pixma_mg3122