Right, I don't care about making money from the forum personally. (I've actually thought about getting rid of the forum ads, since it's often a big headache and the forum has enough reserves for a long time, but operating at a significant loss while there's money basically just sitting on the table feels wrong, even if the level of loss is sustainable for quite a while.)

The things on the forum which encourage spam are allowed mainly because it's part of the forum's mission to be as free as possible. Eg. banning bounties would undoubtedly reduce spam, but that'd be destroying an entire economy/population/culture which has been able to develop due to the forum's freedom. I am willing to take this sort of action, but only as an absolute last resort. It's always preferable to handle these problems by reshaping the environment to make them non-problems, rather than removing some freedom.

It's wonderful when someone is able to constructively do something on the forum instead of continuing with whatever they were expected to do under the status quo. Enabling that sort of thing is exactly why Bitcoin and this forum were created. Though bitcointalk.org is not a worldwide welfare organization, and people are not entitled to make money.

Limiting newbie participation is very harmful for a community. Newbie jail will never return: I consider the newbie-jail period to have been extremely damaging to the forum. When barriers to participation are too high, then the best people often just won't go to the trouble of joining, and the people who are willing to jump through the hoops are often people who aren't good for the community: people with nothing better to do, scammers, get-rick-quickers, etc. Having a permanent newbie jail policy would improve things a lot in the short-term, but would end up being a fatal poison to the community.

The low signal-to-noise is a real issue which seriously annoys me and is often on my mind. But as you mention, fixing it non-destructively is difficult.

~
An idea I had in this vein was that upon registration you'd have to pick one of two paths:
 - "I want to discuss things"
     = Banned from all money-making/spam-hotbed sections until Jr Member
 - "I want to make money"
     = Banned from the more serious sections until Jr Member
     = You have to pass a quiz before posting which tries to inform you about basic forum rules, how not to get banned, maybe some basic English knowledge, etc. (Quizzes are pointless to stop dedicated spammers, since an answer key will quickly be compiled, but it may help in cases where clueless people are ending up here.)