Having one account as backup, incase your account get's "hacked" is fine. However, using that account while blocked on your first is against Policies, you're avoiding your block.
Also, sockpuppeting is " the use of multiple accounts to deceive other editors, disrupt discussions, distort consensus, avoid sanctions, or otherwise violate community standards – sock puppetry – is forbidden." -Wikipedia.
Abce2|Talk 'Other things" 17:02, May 21, 2011 (UTC)