I got told off for doing this. While it isn't necessarily bad (though certainly has the potential to be), it's not a deadlift. Deadlift gets its name from the fact you're lifting a dead weight. If you don't lift it from a resting position on the ground, then it's not a deadlift.
As you start lifting HEAVY, there'd be a massively increased potential for injury as you're not allowing the weight to come to rest on the ground. From what I've gathered from personal experience as well as logical thinking, the lowering of the weight to the ground phase of doing more than 1 rep of deadlifts is the more dangerous part - hence why you don't often see people lower a very heavy 1RM (at least in competitions).
I'm probably wrong, but think about it