Mercury is not a bank. It keeps your funds spread across many banks where they open accounts on your behalf. Then they spread the deposits around to stay below the $250k threshold at each bank. Same as Fidelity and many others. I would be shocked if SVB was sweeping deposit funds into other banks.

I've heard from a few people today who have Cash Sweep Accounts at SVB: https://www.svb.com/liquidity-management/deposits-and-invest...

Some claim that these accounts are insured/protected up to $125m, but I can't find any info online to corroborate that.

This surprises me. I wonder what the mechanism and incentives are for a bank to sweep deposits to another bank.

How can they do that? They don't choose FDIC limits.