Though not strictly relating to libraries, I believe it deserves mention due to many people’s misconception about security. A recent example was the ranting and raving about how google desktop finds chat logs and web browsing histories, etc. Many people thought Google Desktop was a privacy problem or a security problem. Google Desktop SHOWS you the security problem. These things are on your computer whether Google tells you they are or not. Sure it makes it easier for others to find or abuse, but perhaps that is what is needed for software companies to think more about security. Schneier says it better than I can:

Schneier on Security: Desktop Google Finds Holes.

I recommend reading everything he posts. He is one of the best security writers I know of and his posts are often timely and informative. Even more so now that he has a blog. I’ve been a long time reader of his Crypto-gram prior. On a side note I’m pretty sure some browsers let you choose to disable caching of data from encrypted pages. This should be a default though.