Given the stuff flooding the forums, I understand why this was done.

However, I'd also bet there are many non-troll, non-newbies who have not made 50 posts.  If the software allows it, I'd suggest opening posts for accounts that have existed since before the media coverage got tons of newbies interested in bitcoins.  Someone that has been on the forum for a month is probably not crap-flooding the forum.

NOTE:  This does not include me.  My userid was created today.  But, that change will probably relieve the potential upset of a number of users who are not going to troll and who may have useful insight if they decide to post.

It appears that many of the troll flood posts are either trying to simply drive people away or do things to help manipulate the trading.

Both of those should be stopped. 

Of course, some of the flood posts are legitimate newbies asking for help.  Unfortunately, the forum is not conducive to searching and the wiki's aren't non-geek friendly.  The recent press is driving many of those here too.  This is currently, THE place to get help and learn about bitcoins.  Unfortunately, the forum search does not make it easy to get at that collective memory for even those who bother to search before posting.  Think about the new user who is waiting hours for the block-chain to download but doesn't know what a block-chain is or why it has to complete.  Even if they are going to try searching before posting, they don't have the vocabulary yet to search, and I suspect that search would return many posts/threads that would not be helpful even if they had the vocabulary.

It's a challenge.  You risk driving people away, yet the current solution is better than the alternative.