Opera is not the most widely used web browser, and this is common knowledge. The browser has some of the smallest market-share of any major browser. Most estimates suggest it makes up about 2% of global web traffic, if even that. What many people don't consider is just how much functionality Opera includes as standard. Back in 2006, the browser was the first to include BitTorrent support natively. You can use Opera as a full fledged torrent client if you want to, thanks to this functionality. This is one of many features Opera has, which people tend to leave unused. Others include the Opera Mail client, Opera Dragonfly and Opera Turbo.
Turbo is an interesting feature, taking some of its inspiration from Opera's Mini web browser for mobile devices. Opera Mini compresses data to allow you to browse more quickly on a poorer data connection. and Turbo simply takes this feature and brings it right over to the desktop. When the button is pressed it enables compression, redirecting the traffic through Opera's own servers to let it reach you. The concept is pretty unique and tends to work well enough if you don't mind lower quality images as a result of the compression. Opera can obviously provide a more clear explanation of their own work, available below.
Lower quality images ought to be the last things on a pirate's mind. Some countries, including the United Kingdom, have attempted to block The Pirate Bay. Their successes are questionable, with other domains and a proxy from the UK Pirate Party allowing you to bypass it in about five seconds. It's not the most effective block and Opera might just have unwittingly given users another way to bypass the filters.
By enabling Opera Turbo, and then trying to go to The Pirate Bay's site, you can zip right past the blocks. Whether this would work in China, with its Great Firewall, isn't clear. The possibility is there but you might not be able to get anywhere with it. There's no telling how long this exploit will survive for, but it's surprising it hasn't turned up sooner. With the traffic being rerouted through Opera's own servers it is probably confusing or difficult for a government to monitor or track. Coupled with the small market-share it is possible that governmental monitors might not even consider checking for this type of traffic.
Don't expect it to last too long though. Opera could argue this is unintentional or they had no idea about it, but at the end of the day when word gets round it'll probably be dealt with. Yeah, you use it for legitimate torrents, but the site has a reputation for other kinds of downloads.
Source: Torrent Freak