I said for practicing licks, memorizing scales, it's a very good idea. Because it implants it into your mind.
It's like driving a car and talking to a friend in the passenger seat or playing with the radio (I know this has caused accidents). But it's not like you bring the car to a halt to talk or change the station because you already, subconsciously know how to drive, you aren't thinking about how much pressure to put on the gas pedal or stuff like that. You don't have to have your 100% attention on the road (even though you're supposed too). Ok, driving is a bad example, but you get the rift of the idea.
That's why they say, once you learn how to ride a bike you won't ever forget. Because, it's implanted in your subconscious mind. You don't get on a bike and go, ok, I have to balance on to wheels, turn these pedals, and steer all at the same time. You just do it.
And if you practice guitar this way, you will memorize things much faster. It has helped me immensely.
Sometimes I hit notes only dogs can hear.