If you have stealth and are on an object, can it be picked up from under you by someone with super strength? Thanks for reading.

It can be, yes, but sometimes it's more trouble than it's worth. An opposing figure coming adjacent to the object/figure square must stop, and because his movement was forcibly ended he is not able to pick up the object during that action. He may pick it up on a later turn, but to do so will first have to make a successful breakaway roll---once that is done, he may pick up the object and complete his move action. A figure with Charge would be able to attack after coming adjacent, but still could not pick up the object right away. But after later breaking away and picking up the object he would then be able to use that object in an attack if he wished to do so.

If the figure coming adjacent had L/C, Phasing, or HSS, then he would not have had to stop and so would have been able to pick up the object during that first move action. Note that these things would be true if the figure on the object did not have Stealth.

What if the person was taxi in? Couldn't the figure then pick-up the object?
Also not sure but, I heard that th ruling now stands that a charging charcter can not pick-up a object in a square adject to a figure and then charge into battle.

It wouldnt matter if the person was taxi'ed in or not. The act of picking up an object occurs during a move action. If the (what would be the term?) Taxi-ee is adjacent to the opponent's figure he would need to break away (or have L/C or Phasing or HSS) in order to pick up the object.

The clarification with Charge was that you cannot pick up an object adjacent to (or under it usually is) an opponent's figure. As soon as you cross the line of the adjacent square your movement stops and you no longer have the ability to pick up the object. Here's the FAQ
If you can get that object before you come adjacent to the opponent you can pick it up.