Yes, Keri and I both have a handful of stories from writer's conferences, and files full of the business cards, promises, and rejections left in their wake. I'm not slamming conferences in general; I can recall many absolutely fabulous conference experiences. Rather I'm speaking more to the mindset with which some approach them. I know I did. I really thought I'd made it at my first conference when a very nice Senior Editor at St. Martin's sat by a fireplace with me and said, "Wow. You're a real writer, aren't you?" Then, although it was not her practice to do so, she asked me to send her my entire manuscript, not a synopsis and three chapters. She was very professional and I hold no ill will over the rejection: that MS was not ready for prime time. The reading sample was perfection, and many parts of that book still strike me with awe when I read them, but the middle sagged and still does. But that was my first novel, and if I ever choose to rewrite it, I will know what to do.
At another conference I met with the Senior Editor of a small press who all but got into the specific amount of the advance check. This one never even replied, never used the pre-stamped manilla envelope to return the MS. Nice. I fantasized about showing up three years later when this person blew back through the area to accost him at the Q&A with the following query of my own: "What have you done in the past three years? I've created two human beings and written another novel. Can't get your ass to the post office can you?" Of course I never did that, but thinking of it was great therapy.
So take heart: there are the times when you're naive and unready, but there are also the times when you're the together one and they are a-holes. And if you know which is which, you can probably handle self-publishing just fine.