A specialist in document and data destruction in my networking group brought this up months ago.
It's important to note this is **only** in higher quality printers that actually have a hard drive, most home desktop printers operate only from memory.
It's also only an issue when you have it serviced or discard the printer. There are services in place that will swap out the drive for you before you sell it and certify the destruction of the drive.
This is another topic covered by Red Flag Rules legislation [webmasterworld.com]. The core of this legislation is that you have procedures and policies in place that outline how you manage and destroy customer data and what your policy and plan is in the event of a breach - printers that retain data passed through them are electronic documents, they are included.