Reading the particular rules of a bounty as stated by Royse777 will let you know if you are able to use multiple accounts in that bounty. Noone is saying do not have multiple accounts. Managers just have rules that they expect everyone to follow.

Some managers allow multiple accounts, some don't. I think most bitcoin paying signature campaigns do not allow a user to have multiple accounts in a campaign. Bounties are where that rule is much different. Some allow multiple twitter accounts, some allow multiple facebook accounts, and some allow multiple accounts in anything they are paying a bounty for. It's all about reading the rules.

This also goes both ways when it comes to the scambusters. They need to read the rules of a bounty before outing users that used multiple accounts and trying to get them tagged.