Need one more ethernet connection...plug and unplug to devices bad or...

...Or should I just breakdown and buy a $16 switch? (I need one more connection to use on a device. When I do so, I don't really need my connection to PC. So will unplugging the PC connection and putting it into the device I want to use a bad thing?)

Certainly nothing inherently bad about just swapping connections. You'll quickly learn which of the applications on your PC respond gracefully to network changes, and that may or may not lead to frustration. If the switch is a squeeze on your budget, try just swapping connections to start.

There's nothing inherently wrong with plugging and unplugging, but this does put wear on the cables, and they're not typically intended for high-traffic use in this way. If you're doing it once in awhile, no biggie, but if it's daily or more often, you may end up spending more on cables than you would on just buying a switch in the first place.

(The little locking tabs on the cables have a nasty habit of breaking off, making subsequent connections unreliable.)

Thanks for the advice folks. Went with a switch.

Good, like Malor said that will save wear on the connections and also be less hassle for you. Win-win for under $20.