Hi Carroll, I've used quite a few forums over the years, and tend to find it is hard just to get the courtesy of a reply (to the initial enquiry) let alone the situations you described. A simple 'thanks for the enquiry, but....' would seem like good manners, particularly when those individuals actually posted asking for lyricists. I'd like to stress I'm referring to other forums at this point.
It can be a long and difficult process finding people to work with, and as has already been stated, building a rapport, establishing a good working relationship, building mutual trust and respect - it all takes time. And that's assuming that you both like each other's work in the first place. I often find that creative people just want to write (which I can understand), and often don't want to think or deal with the 'business end of things,' and that's where many (in my experience) writing partnerships tend to fall flat.
Like many on here I am sure, I have been burned, ripped off, unfairly treated - but I've had some good and rewarding long term collaborations too. Unfortunately, you just don't know until you take the plunge. One thing I tend to do now, is agree to a 'probationary' project (with a few essential terms agreed) just so both writers can get a feel for each other, and if the signs are good, and both parties are enthusiastic, then a formal agreement can be drawn up, and the serious work can begin. It isn't a guarantee, obviously, but at that point, I don't look past the probationary project - I look at it as a one off gig. If someone proves to be difficult to work with, or their work isn't what I'm looking for (and it works both ways I accept), then no worries, nothing ventured nothing gained.
I know it can at times be soul destroying, but over the years you become sanitized. You accept the bad with the good, and you press on regardless - out of love of what you do. Eventually, you will find that 'team-player' and you'll both fit together like a hand fits a glove. I wish you the best of luck.