Other Palantiri?

[The Might]

Well, just read through the essay in UT again anf two quotations I found interesting:

Actually they must normally have been used by such deputies. Each Stone had its own warden, one of whose duties was to "survey the Stone" at regular intervals, or when commanded, or in times of need.

It must however be noted with regard to the narrative of The Lord of the Rings that over and above such deputed authority, even hereditary, any "heir of Elendil" (that is, a recognized descendant occupying a throne or lordship in the Númenórean realms by virtue of this descent) had the right to use any of the palantíri. Aragorn thus claimed the right to take the Orthanc-stone into his possession, since it was now, for the time being, without owner or warden; and also because he was de jure the rightful King of both Gondor and Arnor, and could, if he willed, for just cause withdraw all previous grants to himself.

And about the Elendil-stone:

One only remained in the North, the Elendil Stone on Emyn Beraid, but this was one of special properties, and not employable in communications. Hereditary right to use it would no doubt still reside in the "heir of Isildur," the recognized chieftain of the Dunedain, and descendant of Arvedui. But it is not known whether any of them, including Aragorn, ever looked into it, desiring to gaze into the lost West. This Stone and its tower were maintained and guarded by Círdan and the Elves of Lindon.

So, as a conclusion, it seems that Aragorn was indeed at that time its rightful owner, while the Elves were its appointed wardens.
Considering the last quotation, I guess that Men no longer were supposed to look to the west and so Aragorn gave up his hereditary right and gave it to its wardens.
Why exactly the Elves took it to the West, I can only guess. Maybe Men were not meant to gaze in that direction any longer, and I doubt it that the Elves took it for personal use.
The Elves were leaving the world and the Undying Lands would become a legend for Men. Perhaps the Elves thought it was for best that Men forgot the existence of these places.
Imagine if an Ar-Pharazon-like Gondorian ruler (because it seems clear things would not stay perfect forever in M-e) looked through the Elendil-stone, saw the beauty of the Undying Lands and tried to reach it with his ships.
I believe this was done for the sake of Men, not out of greed.