There should probably be a flag type for a journal that the creator sets. Suggestions are:
bits or dropdowns:
[open] - no restrictions (default)
[adult] - content contains adult material and should reject anyone whose birthday (yes this can be faked, but still..) is below 18.
[nudity] - content can contain potential nudity
[explicit language] - contains potentially vulgar language and situations
[cryo] - abandon all hope ye who enter here
along with subsequent icons representing this when, for example showing a community
([user icon] username (posting in [user icon?] community)
the 2nd user icon doesn't really make sense for a community, and would be a perfect place
for a 'rating'.
This would help prevent certain 'lj abuse' issues that have occurred, as well as protecting lj with a self-governing rating system that is optional for people to participate in.