Recently, I wrote about a maximally connected resource-oriented alternative to the OSGeo Tiled Map Service (TMS). Readers mainly objected to the double request: one to get a map image tile, one more to get links to its neighbors or links to higher/lower resolution. Is this prohibitive? Without trying, I can't say, but it does occur to me that more sophisticated enterprisey systems might use JPEG 2000, with URIs of neighboring tiles stored in the JP2 XML box. One request per tile, and I'm still using hypermedia as the engine of application state.
If JP2 + XML is good enough for T.J. Hooker, Jr. (top of the article's lead-off graphic), it's good enough for me.