Any merchant should protect their point-of-sale environment to the same level as the rest of their cardholder data environment. Maybe even a higher level since the POS's are more vulnerable to physical threats.
IBM Security Services PCI Blog
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Andi Baritchi 27000216AA firstname.lastname@example.org Tags:  dss pci malware anti-virus appliance usb point-of-sale 643 Visits
If they see cardholder data - YES. Check out The TJX Effect and Keeping Point-of-Sale Equipment Secure for the rationale behind this.