I doubt it'll stop the spam since those newbies sooner or later are going to become Jr. Members (quite often by farming their accounts in other sections). TBH, this would just hurt legit users more than it would the spammers. One of the staff suggested excluding the Bounties (Altcoins) board from activity calculation / post count which I'm totally for.
I'd like to expand the idea as follows: Ban/remove any bounty campaign that does not use Google Forms (or similar) for submissions. Using this is: a) More efficient. b) Doesn't spam Bitcointalk with useless enrollment posts. @mprep should take a look at this.
Seems a bit too heavy handed. As I mentioned, I'd rather the Bounties section simply not contribute to the post count. Doesn't punish the legit users who are there to apply to bounties but doesn't allow the spammers to pad their post count / activity.