From AnimeSuki Wiki
In the past there was little to fear when you were involved with copyright infringement regarding anime (such as fansubs). If anything it would be the fansub group or site hosting the fansub that would get nastygram from a lawyer or company representative. However in the past few years individual downloaders have also become a target.
It started in late 2007 when Odex, an anime company from Singapore, hired BayTSP to target downloaders of series they had licensed. As it turned out, BayTSP misinterpreted their request and started sending out notices to downloaders worldwide, even though Odex was only legally allowed to target illegal downloaders in Singapore.
However about a year later the original Japanese studio's have also learned to use BayTSP's services, and as original copyright owners they have the full legal right to act on copyright infringement of their intellectual property everywhere in the world.
It's important to note that not every downloader of the affected series has been getting these notices. It kind of depends who BayTSP is sending notices to and which ISPs actually bother to act upon them. However if you don't want to receive a notice it might be best to use a download method other than BitTorrent (such as newsgroups, direct download or IRC) or avoid downloading these series altogether.
Some downloaders have reported they've received DMCA notices for the following anime series:
- Aniplex (Official Site • ANN)
The following internet server providers (ISPs) are known to forward DMCA notices from BayTSP:
- Vidéotron ltée 
- Demon Internet 
- J:COM NET 
- Pacific Internet 
It's important to point out that if you receive a DCMA notice for downloading anime it does not necessarily mean that series is licensed, especially if such a notice is send on behalf of a Japanese anime studio. Unless AnimeSuki itself receives such a notice or if it's been licensed by a company in the US for release on DVD or Blu-ray, we will not remove any affected series.
BitTorrent is an insecure protocol
Face it. Any time you download a torrent, your BitTorrent client contacts a tracker which holds a list of IPs that are also downloading the file(s) in question and adds your IP to this list as well. This is the primary source of evidence for BayTSP. Also note that encryption won't stop this; encryption will only (potentially) prevent bandwidth throttling but it won't hide your IP from BitTorrent trackers. Furthermore IP blocking tools like PeerGuardian will not be of much help as your IP will still be broadcast to other downloaders by the tracker and companies like BayTSP change ISPs all the time making them hard to block.
If you have also received a DMCA notice and/or would like to discuss this topic, check out this thread on the forum.