Question: a few weeks ago, we setup a cronjob that wipes the entire contents of /tmp every Sunday at 5am. I wasn't really convinced that this is a good idea. Today we discovered that a certain task depended on an existing directory inside /tmp - the task was broken, and worse, it remained silence about why it failed. The question is:

Is it generally a bad idea to just wipe out /tmp?

Answer: 
It depends a bit on applications and distributions. It's typically safe to wipe /tmp on reboots. Wiping it on a running system is very likely to break applications. /tmp is not meant for permanent storage, and any application using it for such is serious broken, but applications can easily leave files in /tmp for months on a system that stays online. Which is why I am a bit suspicious about tmpwatch. 

In the end I only tend to look into how much is stored in /tmp when a server is running low on hard disk space. If there is plenty of HD space why bother?
My thoughts on this is..

Yes.. dont wipe the /tmp..

Lots of strange and weird applications use the temp for buffering and temporary storage..

If the information wasnt important, it wouldnt store it there :)

Ive seen, logging buffers, webserver sessions and even library versions in there on servers..
Its best that you leave it alone.. unless it needs to be cleaned...

Hope this helps :)