The Pinterest connection is that it is serving a largely female audience with interest in crafting and recycling content. Basically, if MakerBot and Pinterest joined forces, this would be the likely result.
The connection, as I see it, is that Pinterest user's primarily interact with the service by "repinning" other content. Only 10% actually add new content from other sites, and would wager a minuscule portion upload new photos from their desktop.
Cricut users express their creativity by cutting out content that was already flowing through the system and expressing their creativity in arranging the cut-outs, much the same way people create Boards on Pinterest.
There's a big gap in people sharing digital goods and wanting the trinket on demand, and another gap to getting the 3D content widespread enough. Those are big gaps.
Less so: They figured that any products which primarily target women must be fundamentally similar.