Babies love to master a new skill. Once they do it, they want to do it again and again. The danger at the top of a flight of stairs is obvious to most parents, but keep in mind that if your baby can climb up a flight of stairs, which may happen before he learns to walk, once he climbs up he can fall down. Keep gates at both ends of a flight of stairs to protect your baby from falls.
Walkers are a great diversion for infants, but they provide no developmental benefit.
Infants don't learn to walk by being in walkers. A walker may provide an infant with a significant increase in mobility which can be a danger if he is left unsupervised even briefly. An 8 month old scooting around the room at lightening speed sitting in his walker may have access to items on shelves or table tops which he couldn't get to previously. Walkers are a particular danger near stairs. When a child falls down the stairs in a walker, the walker prevents his natural protective reflexes from breaking the fall.