Yes, your account will be automatically flagged if you fall below that amt. It is a hard number as the computers flag your account. It is recommended that you deposit 30k if you intend to daytrade stock. If your balance does fall below that amt, it DOES NOT prevent you from trading other asset classes, i.e. futures or forex, so if you trade more than just stocks and options, you have other alternatives if you get flagged.
Nipapage, You asked some excellent questions - that I was myself looking into few months back. I am wondering if you have figured out a way - if yes, it will be great if you can share your experiences with the community. Best, -R