Is it bad to keep my iPhone plugged in even at 100%

Also think of all the electronic retail stores like the apple store or best buy that leave their display versions plugged in at all times. Even in the apple store all their devices are always plugged in!

No and no

No I was actually at the apple store and I asked someone that exact question and they told me that it's perfectly okay to keep your phone plugged in about an hour or 2 even though it is at 100% so you can let the battery level out and he told me its good for your battery because it will hold more of a charge.

I don't know if that makes sense but that's what I was told

You could but not all time cause he told me it will damage the battery and it would hold less of a charge

And yea that's what I do and my battery is okay

Nonsense - people leave all sorts of similar Lithium battery powered electronics plugged in overnight or for longer periods of time. Leaving your iPhone plugged in overnight will NOT harm your battery at all. Mine and the 3 before it have spent every night in their charging stands beside my bed. The iPhone, like almost any modern solid state device, has built in overcharge protection (the charging circuits shut off once the smart battery reports fully charged, and they do not come back on until the charge state has trickled back down to 8-12% discharge or so, which takes days for a health battery in a device running on charger power).

Do you unplug your laptop computer once charged? Your iPod? Your tablet? Your portable GPS? Do you get up in the middle of the night and make sure to unplug your Nook or Kindle once they are charged? Or any other smart Lithium battery powered device? Of course not, because it is completely unnecessary to do so and will not harm the battery to leave them until it is convenient to unplug them, or you need to unplug them to take them with you.

Absolutely. Worriers might also consider modern wireless house phones. They use the same battery technology, and are never disconnected from the charger except when you pick them up for a call.