What you are viewing is a typical Network / Data Rack. It measures 22" wide by 7' tall.
The rack shown is supporting about 20 devices. 10 IP Phones and 10 computers, plus wireless devices.
This helps illistrate the room required to be set asside for the heart of the business. The front should be unobstructed, and about 1 foot on either side for access. This rack also has a business class UPS sitting behind it, on one of the support feet.
At first glance it may appear to be over kill. However, when growth begins to occur, it provides the space to do so. This site added 20 more offices, and required another patch panel and 24 port switch, as well as adding cameras and a DVR shelf.
Mounting the equipment to the wall is not only unsightly, but hinders working on the equipment and increases the time to work on it. We find, someone will put something against the wall in front of and below the wall mounted equipment as well. This obstruction creates more issues which will only add to time to work on issues.
We find a percentage of time, sites experience cronic unsolved issues, solely due to the people and how the equipment was installed.