Entanglement of large molecules
Well, very long hydrocarbons can become twisted around each other. This is definitely known in the polymer literature. Consider some branched polyethylene with ~1,000 repeat units. It's not too hard to imagine that multiple chains can become entangled in much the same way as shoelaces or strings when you mix a lot of them in a box.

You are also right that with large molecules, there are more sites for intermolecular interactions. Consider that there is a "combination" effect with lots of sites. That is, to pull two very long linear chains apart, you need to break lots of interactions.



Notice that pulling one atom on the bottom away from its neighbor on the top chain will require the movement of all atoms on the bottom chain. So it's slightly harder to separate two long chains, not only because there are so many interactions, but also because of the combination. 

Put simply, the difficulty in separating the two chains is slightly higher than simply the sum of the interactions.