I wouldn't post a rough draft. If it was edited, and proofread so there's fewer flaws - I'm certainly open to the idea. Feedback, can smooth out the rest if there's any left.
However, there are quite a few writers of serial novels who post entire books on the net. Manage to get a publishing deal despite having the book online. Some, simply self publish when it's done. Making sure the published version is error free and has some kind of incentive.
Some writers, choose only to put samples up. But, if a pirate really wants to spread your book around - they will. So, it's not any less dangerous in my opinion. And, there are ways to reduce the odds of it happening.
I do believe, it is paranoia to think people will plagiarize an entire story. For many reasons. One being that you don't need to display copyright information to be protected with a registered copyright. So, anyone who plagiarizes a site or blog takes a huuuuuge risk.
However, I do agree it is better to register a copyright for your work or possibly as a publisher if you want it to be commercial.