Once the group's Obligation is laid out in table format, and the GM rolls at the beginning of the session, there is always the chance of a "doubles" roll, thus doubling the Strain loss to everyone.
But because of the way %'s work, and where doubles can hit on a chart, some PCs can be immune to being hit directly with the doubling penalty.
For example, in a group of 6, where PCs are going to have - at most - 10 Obligation to start, the first guy on the chart cannot have doubles hit his Obligation. Somethimes others as well.
01-10 | PC1 | Debt
11-20 | PC2 | Addiction
21-30 | PC3 | Bounty
31-40 | PC4 | Debt
41-45 | PC5 | Favor
46-50 | PC6 | Dutybound
On this table, PC1 and PC6 will never have a risk of suffering 4 Strain.