This is a set up from the Hennessy site:



I feel like I've heard someone mention using their bike as one of the hammock supports, as well, so you might get by with only one tree/post/whatever if you went that way.

My only concern with the ground is under-insulation. If you're using the typical underquilt set-up, it won't be much good for ground sleeping, and carrying a pad for the few times you might have to be on the ground seems like a waste. But it does seems like it's doable. I've hung my hammock in some odd places, but I always managed to hang. One time the trees were so far apart and of uneven heights that my butt was dragging, and then I did have a pad, so I put it under me, but most of me was off the ground.

I have thought about something like this: Handy Hammock

Just in case. If you could reliably use your bike to hold up one end, then you'd only need half that set. But even though it breaks down fairly small, it's still an awkwardly-sized piece of gear that may not actually get used. Still, it's on my wish list. There are some places I camp regularly where my camping location is dictated by the trees rather than by where I'd like to camp.