They're subsidizing risk in a cumulative manner. When you hold things on your books you're subject to overnight risk (i.e. a big move can happen when there is n

They're subsidizing risk in a cumulative manner. When you hold things on your books you're subject to overnight risk (i.e. a big move can happen when there is no liquidity to move something because markets are closed). This can be managed by position sizing, hedging, repo ops, etc. If you have ~~unlimited~~ consistently increasing/available, government provided repo money available, you get to take more risks and don't need to buy other forms of insurance. So there is some cumulative impact to argue the point, but like you said it's not the sum of the loans. That said, I don't think this bodes well if you're in the camp that thinks the bigger the bubble the bigger the pop.