It may seem like a funny question but having been on the NEO forum, it seems a few of my anime titles may in fact be illegal copies something which seems to be rife.
I had my suspicions about a copy of Clannad After Story that was billed as the Japanese Version - well they all are just subtitled - which arrived with a big sticker over from Anime MegaStore which when I peeled it back revealed it was region zero and was issued on two cd's whereas the US version used four as did the UK so some highish degree of data reduction was being used to squeeze the content into each disc. The discs were made in Malaysia.
I also realized after checking my Haruhi Taiwanese set was bootlegged too as the official set was Region 3 and again spread over four discs. That one had a stop/start problem for several minutes and as the UK distributor has just re-issued their version four discs I've replaced the Taiwanese import with there's although it's in PAL colour.
I have ordered up the Complete four dvd set of Clannad Afterstory which also has a dubbed soundtrack option to replace it
It is my intention that as soon as any other discs of questionable origin are found and authorized replacements have been identified to replace them all.
The funny thing is that some of these titles for all of that compression do look reasonable compared with either Digital TV or 360/480P streamed pictures which suggests the encoders they use are rather good although when you get a lot of activity you may detect the odd artifacts
And there is this: Some titles have yet to make a Western Version R1 or 2 or like Cardcaptor Sakura don't have readily available dvd's as they were only out briefly. I can't help but wonder if these bootleg titles exist at least in part because they fill a void in the market that could be tackled through simple bare bones packaged sets issued here or in the US.
One things for sure it's often easier to find these copies in search than anything kosher.