I agree about the 360 second rule and also the 'you already posted this' bug. They are very unfriendly for newbies. As more people who are not 'very tech savvy' become familiar with bitcoin, they will come across this forum which is a massive aid for newbs to BTC. It nearly chased me away when i got these messages (in fact it did for that day but stubbornness made me come back again the following day!)
I agree that many newbies come to bitcointalk to ask their questions, but it is indeed not that hard to wait 6 minutes before making your post.
Also, we will have a lot more spamming if people can register an account and make 10 posts in a minute.