Some uploads just use a random file name now making it impossible for MPAA, RIAA, etc. to just simply search usenet posts for their content. If you don't have the NZB then it's unlikely you'll find it. Also if you use the european usenet providers they typically don't comply with DMCA notices and have more complex take down procedures.

Sickbeard is faster than the takedowns by a solid 20+ hours if your computer runs 24/7. As I said its very much dependent on how connected you are - access to high grade nzb aggregator sites in particular.

it has changed, but not nearly as much as "content providers" want it to. namely, it used to provide a wonderful archive for just about any kind of copyrighted material you can think of. usenet providers have been increasing their retention (e.g. 1900+ days of binary retention). so now with the take downs, a lot of copyrighted material is gone within a day or two.

i'm a little bit unsure if this is true, but it definitely seems to be. a usenet provider has "complied" with the DMCA request when they have removed enough of the yEncoded posts to break the file on their servers, including parity repair. different providers remove different posts.

thus the emergence of "block accounts," which are usenet providers that resell amounts of data with no time limit, as opposed to your main usenet provider who chargers monthly. then nzb downloaders (e.g. SABnzbd+, NzbVortex) look to your block server for articles that are missing. well really servers, it's not uncommon to have multiple. the key is to have your block accounts all from different top-level resellers.

http://www.reddit.com/r/usenet/wiki/providers