Looking back, it’s hard to believe the skepticism in the online lending sector that greeted the arrival of Marcus, Goldman Sachs’ online retail lending arm. After a few growing pains, Marcus has hit its stride, benefiting greatly from a parental balance sheet that has no legacy credit card business or branch network to constrain lending. That has freed Marcus to provide flexible terms to borrowers, and in an appealing, old-fashioned twist, Marcus actually makes it easy for borrowers to speak to a human being when they have a question. Amazing, right? We have no doubt that this combination of brawn, brand and basic common sense will help Goldman in its just-announced initiative: lending money to the high-net-worth clients of RIAs and small broker-dealers on Fidelity’s Custody & Clearing Solutions platform.