Does anyone have experience scalling on the same traffic source? for instance if you have a profitable campaign, you make 4 or 5 different accounts on the same traffic source and run your campaign on these accounts using different bids for each.
is such a thing even possible or is it better to just scale on a handful of different traffic sources?
Most traffic sources will not allow the same person to sign up for multiple accounts - at least partly due to the possibility you've described.
However....what's to say we can't help family members and friends to manage their campaigns? 
May require for each family member / friend to fund the accounts using their own CC/paypal, so there's a trust issue there for both parties. May also need to log in using different IPs for the stricter networks. For those of you who are creative you can easily get around this, but I'm not going to discuss anything that goes against traffic source TOS. 
Amy
The scaling strategy is different from traffic source to traffic source and depends highly on whether or not you are hitting your preset cap with the source, the options you have to test new landers & banners, and if you can expand the targeting/reach without causing a decrease in ROI.
The most probable thing that will happen once you scale is that your ROI percentage will decrease but that doesnt matter. Its better to make 10% on a 10K placement than to make 20% on a 1K placement.
Many sources allow simply cloning a campaign, you might want to try that. I sometimes use that, using stacked bids to secure myself a large part of the rotation.