@info75d9201e3c4 - In many cases, the same would happen elsewhere if the billing / authorization department for [insert company] paid as close attention to billing matters as closely as DigitalOcean seems to. Using the same payment method for multiple accounts can raise a red flag in many cases; it's not limited to DO.
No company, small or large, wants to get hit with a chargeback. When a new customer comes through, pays one account off, creates another and pays it off too, all within a short timeframe, that'd concern me as well. Chargebacks don't play favorites. Whether it's $5.00, $500.00 or $0.05, if you get hit with a reversal, as a company, you're paying whatever chargeback fee was defined in your Merchant Agreement (and in many cases, quite a bit more). You can try to fight it, of course, though it's best to do your best to mitigate the chance before the chance has the opportunity to surprise you.
It'd be different if you were a customer of 2-3 years and they were flagging you on payments, though more often than not, the issues are limited to new accounts and in many cases, PayPal (which always raises red flags - for one reason, they tend to be one-sided in many cases).
That said, it does not mean that you, or anyone else in this thread are in any way, shape or form "bad" or that you're going to use your DigitalOcean account for nefarious activities. Thresholds are set and when they are met, whether it's by you or by me, a red flag goes up. I've had it happen to clients I've worked with who routinely paid between $400-$4,000 a month for services with some providers. They share the frustration, but also recognize that if security measures were not in place, the cost of service would most likely be higher, the level of support would be further reduced, and in some cases, they too would be out $$.