http://www.livejournal.com/support/faqbrowse.bml?faqid=49 is no more, since the information is covered in FAQ47 and I don't think the question itself comes up often enough to justify separating it out into its own FAQ.
Your entries always keep the security level you choose, no matter who marks it as a memory and what memory security level is chosen.
For example, your Friend may mark one of your Friends-only entries as a public memory. Anyone who looks at your Friend's memories will see that your friend added the entry as a memory and will see your Friend's description. However, if someone who is not one of your Friends clicks on the memory to access the entry directly, that person will see Error - You are not authorized to view this protected entry. This error will appear any time a user tries to access an entry that they are not permitted to view, even if they can see a link to that entry, such as a memory.
* Removed the "how to mangle the URL to get the memadd link" -- way too complex and not a very common use case, as far as I'm aware.
* Link to FAQ49 removed from the security section
* Took out the "you can't edit the memory metadata for a deleted entry / entry in a purged journal".
* taking out the "entry has been deleted vs. entry in a purged journal" distinction with deleting entries, since purged journals' entries ARE deleted.
* condensed editing and deleting down into one section, took out lots of the fluff text
... and it's still not significantly better, but kinda sorta maybe progress? Anyone got any ideas on other things to tweak to make this easier to grasp?