"It can be dangerous if the program creating it is written wrong"<.
Or by a exploiter trying to inject code into a running proc (program) on the server that has been established and has been deployed on the server; and that has elevated (possible) privileges; thereby inheriting those privileges, which sets up a possible api for the attacker.
Sorry for the 5 years after. I'm in the process of deploying a server. This shared memory issue has been well documented
By default, /run/shm is mounted read/write, with permission to execute programs. In recent years, many security mailing lists have noted many exploits where /run/shm is used in an attack against a running service, such as httpd. Most of these exploits, however, rely on an insecure web application rather than a vulnerability in Apache or Ubuntu< from help.ubuntu.com
But yes as psusi related, coders can write code that does not allow shared memory. But do they, something as important as a server needs to be at least 99% bullet proof.
Linux, own it or someone will own it and you.
Google is your friend