It can also be extremely unhelpful, for example to this chap today on reddit:
http://www.reddit.com/r/Bitcoin/comments/1bd1d1/i_think_i_ju...
Who didn't seem to know about return transactions and seems to have lost 90 BTC on that. (Because he/she used a "secure" live environment that would work with a temporary wallet and just one extra address with his/her money.)
Brain wallets are always a terrible idea, either the pass phrase is too simple and easily cracked, or too complicated and easily forgotten.
Paper wallets are only useful for savings, if you want to spend the coins you should move the full amount.
As said elsewhere, if you use the stock client as designed, and don't use brain or paper wallets, then you should never lose coins.
https://bitcointalk.org/index.php?topic=11104.0;all
That 7208 BTC would be worth about $680,000 today.
There will be a lot fewer than 21 million BTC in actual usable existence after all these errors are tallied!
As long as you use the software in a relatively standard way and don't ever delete your wallet files, you'll be fine.
Some bitcoin clients fix this by using a deterministic generation of new addresses for the wallet.