Well this is excellent thread you started and I was looking forward to answering similar questions.
I got to know about CE from @#-Link-Snipped-# . I got interested, I joined. I liked the place, I stayed and started contributing. I tried to do same thing to my friends, pushing them to join here and learn something. We know the quality of stuff we have is degrading but still we make stuff that is knowledgeable. People don't want that in the college. They want a hard and fast Google. They dont have patience to read and work in Forum threads. Or to put it in perfect way, they are ignorant to the power of Foruming and Social Networking. All they know about social networking is Facebook / Twitter. That is a major issue happening here. they don't want to wait and work on forums. Still I tell every other guy I think would be interested but ultimately only few join.
You came in college on 20th and gave a demo on CE. Many people saw me active there and recognized immediately. But only some joined. Why because they don't understand what actually we are doing here. Awareness i colleges is the biggest issue CE is facing from getting quality people and quality stuff. You make them aware, all will come. And I even told about CE to some young professors, they don't realize even the importance of forums. People don't know what foruming is, that is an issue
Next thing about invites. If you restrict accounts creation, that will slow down traffic according to me. Maybe we get people who make an account once and never return but that overall contributes to stats of the website which everyone gets impressed on. "147k users there? there must be something, lets check it out." More thing we can do is add a friend referral system. You get points for adding friends here (add that clause in CEoM) and people will start calling more and more friends. If they call 10, atleast 5 will think about doing something here.
For the quality of discussions, we should moderate every thread being created. If its worthy, it stays in main section else move it to some other box. So anyone visits a main forum section, he gets a gold mine. And you actually cannot stop spams or useless topics by 100%. What we can do is segregate them.
For inviting the experts, if we identify some people, we can send them an invitation card like official invitation on paper. They will pay attention to that.
Excuse me on this : The name CrazyEngineers is awesome, but for youth, an excellent name but when it comes to a bit older people like professors,aged people who are a bit egoistic, the name seems kiddish and they tend to ignore it. That MIGHT be a factor. Personally, if you see my #-Link-Snipped-# page, I wrote there," I am a Crazy Engineer" and added a referral link there. Its because I take pride in that title.
Experts will need special treatment to keep them stuck up there.
For moderation job, you can add some more people to make more quality content and pay them in points or preferences. Cash is not the preference. It is the first forum I ever saw where you actually pay cash to people for working and contributing here. THAT is a ++++++++ thing. It should attract more and more people. But that ain't happening. Don't know why.
For some new things, Yes a job update app, or something similar news will be very good. But that will be more of spoon-feeding. And college students are accustomed to being spoon fed so we can include that. Apart from that, we really need a chatting system (like you said about CE Conference, i dont know much about it but something will be very useful).
And yes, one last thing. I am trying to recruit as many good people i can here and encourage them to learn because this is where you get exposures. I used to be active on forums and that is where I met my business partners and started a business ultimately. People don't realize its power so we need to make them aware. And all the CEs understand that so they can take this initiative. Rest leave everything on Google. Make some more head meta tags and some basic link building, traffic will pour in. Manage the quality by moderation and we are good to fly higher.