12 months is fine. It shows you've given it a serious shot at a company and it hasn't worked out. Or, for contract consultants, it just shows you're moving where the work is.
If you're working at smaller firms, it's accepted and natural that the workflows can change more sharply than at a big firm which can cushion you from market vagaries. Therefore you need to actively manage your career and move more often.
It would only of concern if you're consistently moving between big firms as it would come across that you're either really screwing up to manage to be booted out of a cushioned environment, or you've failed to recognise that the big-firm environment isn't for you.