The 'burden of proof' is on the plaintiff, since the defendant is presumed innocent until proven guilty. [=the plaintiff must prove that the defendant is guilty]
The 'tax burden' has been falling increasingly on the middle class. [=middle class people have been paying a greater portion of taxes]
For the rest of his life he 'was burdened' with the knowledge that he had done nothing to help them.
(..) I will take it. I will take it. I will take the Ring to Mordor. Though... ...I do not know the way. I will help you bear this burden,Frodo Baggins... ...as long as it is yours to bear. If by my life or death I can protect you... ...I will. You have my sword. And you have my bow. (..)2001 The Lord of the Rings: The Fellowship of the Ring
(..) And yet to have come so far still bearing the Ring... ...the Hobbit has shown extraordinary resilience to its evil. It is a burden he should never have had to bear. -We can ask no more of Frodo. -Gandalf,the enemy is moving. Sauron's forces are massing in the East. His Eye is fixed on Rivendell. (..)2001 The Lord of the Rings: The Fellowship of the Ring