The "paperclips" were never actually paperclips (at least not to the originator of the word-picture, Yudkowsky) but rather tiny molecular squiggles which are a

The "paperclips" were never actually paperclips (at least not to the originator of the word-picture, Yudkowsky) but rather tiny molecular squiggles which are a physical manifestations of the MAXINTs you refer to. In other words, tiling the future light cone with molecular squiggles is (according to Yudkowsky) a likely result of the AI's engaging in wireheading if the AI is free to re-arrange reality however it likes because it is able to overcome any human opposition. In other words, there's no particular reason for the wireheading process to remain tidily contained inside the hardware the AI is running on: it might in contrast result in a vast field of "paperclips" centered on where Earth used to be.