Effects Of Encryption On Computer Systems

(I have read the rules of this sub-site and I think its okay to post but advise if not)

I am currently writing an essay and one part is a discussion about the effects of encryption on an Operating System/Computer/Infrastructure in general.

However, I am struggling to see how a computer would be effected by encryption, whether it be Full Disk Encryption or container based, beyond the performance of the system degrading slightly.

There does not seem to be any other kind of impact on the system itself. Most papers and articles all seem to point to and focus on the performance aspect.

Am I missing something obvious?

PS. I am writing this in reference to encryption using software like TrueCrypt.

Any pointers would be appreciated.