I think the recent media items that you refer to relate to webcams that are not connected directly to PCs, but sit on the (home) network independently. These are then left active and accessible externally via the Internet so that the user can view their home (or whatever) remotely.
In order for this to work the webcam needs to be addressable over the Internet (via an IP address) and connects (e.g. via WiFi) to the router. It's pretty obvious that such access needs to be secured (e.g. via a secure password that the webcam unit use). The problem arises when such devices are left with the default factory passwords.
Your USB webcam does not fall into this category. As long as your PC is secure (e.g. decent AV and firewall as FruitBat says), your webcam should be fine.
The story circulating about this event seems to have been covered by 'Batch', and is mainly based on people not setting a new password, leaving the manufacturer factory password still on the device.
My local newspaper did an article about this yesterday, because apparently it as effected a number of people or locations in my area of the country, out of a possible 500 UK wise. The article also seemed to suggest that the cameras in the main were from Chinese made Foscam webcam's
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