Figuring out this kind of information isn’t easy, but it’s possible, Dumontet says. In order to combat this, most merchants create a unique Bitcoin deposit address for each sale, but when the merchant decides to bundle all of those deposits together — to pay suppliers or to convert Bitcoins to U.S. dollars, for example — they could still be giving a competitor a way of tracking all their Bitcoin transactions.
So a competitor could learn something interesting about a company by first paying them in Bitcoins and then tracking how that money flows through the block chain — Bitcoin’s public ledger — and studying the other transactions that got bundled with the competitor’s original payment.