Should I get a kitten from Craigslist or adopt from a shelter?

Me and my boyfriend just got a new place and in a few months I am thinking about getting a kitten so my cat I already have isn't lonely when me and me boyfriend are at work. I adopted the cat I currently have from a shelter 2 years ago. She is extremely energetic and playful and still acts like she is a kitten so I thought a kitten would be the best choice for her, but I'm not sure where to get it from. Obviously adopting from shelter is good but is there anything wrong with getting kittens off Craigslist?