they dont go out of balance. There is so little mass to them that they cant really affect anything. Now if you have a mismatched B&M weighted flexplate, sure but not stock. What motor and chassis is this in? have you checked your spark plugs and leads?
No. A shake as you accelerate is more likely a dead or weak cylinder. Imbalance will create a shake as soon as the rpm is reached. you don't always have it at idle, but usually as you free rev it out of gear the imbalance will get stronger as rpms rise.