In this new era of supposed financial sobriety, consumers are putting less on their credit cards — often because they can no longer get credit cards. But if you really want to buy something online, you can still get credit. People are reaching for alternative forms of credit: Sometimes they’re using their debit cards to overdraw their bank accounts; and sometimes they click on “Bill Me Later,” a service — now owned by eBay — that does just what it says. Thing is, if you’re late with a payment, the interest rates are punitive — and now some consumers are suing, saying it’s a new form of disguised usury. And the case is making some consumer advocates say maybe people should think twice about moving away from credit cards.