My laptop has a three prong grounded plug. Does it need the ground pin?

You wouldn't experience any problems except in the rare case that your laptop has an internal short from a live power line conductor to an exposed metal part of the laptop.

The ground plug is purely for safety and has no effect on the proper operation of an electrical appliance. It accomplishes two things. First, it assures that the plug is inserted with the proper orientation so that the hot wire of the socket is connected in a predictable way to the appliance. Second, the safety ground wire is typically used in appliances that have a conductive case and the case is connected to the safety ground. If a short circuit were to occur inside the appliance, any current will be passed through ground, rather than through the body of someone who touches the conductive case.

The laptop will work just fine if the ground plug is removed or if the hot wire and neutral wire are reversed.

To answer the title of you're question, you may not want to remove the grounding pin because "If the customer alters the product in any way, then all warantees are void. It is, by definition, the customer's fault, whether there are technical reasons or not."

As long as you aren't using a microphone, there is no issue.

But if you are, you will likely get mains hum while plugged in if you don't have a ground.

Laptops that only have 2 prong power adapters often also suffer from mains hum on the microphone jack or a usb mic. when plugged into mains. only the built in mic next to the webcam will be hum free because of how it's isolated.