It was the signature campaign that is profitable but not always anymore.  Many bounty campaign shifted to twitter and facebook as their major allocation for bounty.  Aside from that in signature campaign your account can only apply for one campaign while on others, you can apply to different project bounty campaign making your chance of hitting a huge pay bigger.  In signature campaign, once it joined a failed campaign, all the time passed had been wasted while in other bounty, since you can multi campaign, the loss is not that significant.