To kovidgoyal: I've bought a VPS and I download some RSS feeds/articles with Calibre once a day before I wake up and send them to my Kindle. And now the reason: I'm from small country in central Europe, the VPS in the USA, and I downloaded it, of course, without advertisements from my country newspaper's servers, not like a common visitor of those websites.
Maybe I'm paranoic, but it's better that prohibited IP address of some IDS or something like that. When Calibre identifies itself like a common browser it's impossible to identify it
Of course, I use wait intervals and the script goes every day in another time.
I hope you understand me
BTW: Calibre is cool, I'll donate it