The downside to using an ungrounded outlet is your less protected against a power surge since there is no where for excess power to go when a surge comes down the line. When a power surge comes down the line it needs some place to go and that's what the ground wire is there for. You can always sever the connection buy the use of a surge protector but they less effective on ungrounded outlets since all they can do is pop their breaker but with no place to discharge the exta electricity it may still jump the breaker and damage equipment plugged into it. Just a note just cause you have a 3 prong outlet does not mean the ground is actually connected to anything. Most surge protectors will indicate if the outlet is indeed grounded or not.