Personally, I love my jeans. I live in them and find them super comfortable. That said, I can't imagine going the extra mile and trying to do yoga in them.
Second Clothing, a Canadian based clothing company, has created the Yoga Jean ($120), a new line of denim that combines fashion and comfort. Yoga Jeans are perfect for a lifestyle where the emphasis is on being cool and comfortable, and where flexibility and relaxation are part of daily life. Offering the flexibility of a yoga-like garment, Yoga Jeans made from 3% elastane, establish a unique balance between the 5-pocket jean and the comfort of the yoga pant. I think these jeans would be fabulous for anyone with an overly active job (like stay at home moms, for one). Or maybe for those times when you know you're going to be doing a lot of moving. For example, often I like to walk home from work but it's hard to do in my other jeans, so the Yoga Jean would be a perfect fit (no pun intended) for my treks home.
Keep in mind, jeans are jeans, no matter how you cut 'em. I love the idea behind the Yoga Jean and I love that if in a pinch, these jeans could float you through your yoga class more than any of your other pants. However if given the choice I would recommend wearing yoga pants over the Yoga Jean to your yoga class. For more information, including how to buy them, visit Second Clothing online.