The reverse is also true - we might gain upside if the price continues to Skyrocket - but how do you protect yourself from this?
What if they have an agreement with one or more exchanges, and complete the transaction by satisfying the current highest bids?
If all your customers paid in BTC, it's very true that you might take on an unacceptable level of risk. But as a practical matter, accepting BTC as an alternate form of payment might be a great way to diversify your holdings.
However, some businesses currently could suffer if they accepted Bitcoin due to it's volatily. If you're selling SAAS your cost is tiny so accepting a more +EV payment currency is probably beneficial.
However if you're selling physical widgets on very slim margins and don't have anything in place to reduce your exposure via quick selling of Bitcoin, and cashflow is/could be an issue it's probably not suitable.
If you go with the first option, nothing is really different. You accept bitcoin, but you get the payment in your currency.