Amplification also pegs the responsibility for technology’s impact squarely on us.
Blame, pin upon, hold accountable
These are the nearest meanings.
Note: Finding many examples of this usage on the web but not authentic source as yet, still looking, will edit as soon as I find one.)
It pegs the responsibility entirely on some vague and nebulous “them”.
The new status of the case, in effect, pegs the responsibility for commissioning the crime on a single culprit.
It means 'affixes' or 'attaches' or 'fastens' or 'pins'. So, 'Amplification also fastens the responsibility for technology’s impact squarely on us.'
Several of the definitions I found online for 'peg' included a verb definition something like 'to fasten or attach with pegs', but didn't include the idea that the peg itself might be metaphorical rather than literal. However, wordnik has a simple 'To affix or pin' definition, and definition #12 on dictionary.com has 'to fasten with or as with pegs' - of which this is the second option: 'to fasten as with pegs'.