Yeah, I think one word tags are annoying. Here's a quote from the tags help page at del.icio.us:
The only limitation on tags is that they must not include spaces. So if your web page is about a two-word place like "San Francisco", you may want it tag it as sf, san-francisco, SanFrancisco, san.francisco, or whatever else makes sense to you. You probably don't want to use commas, though, since a comma will be become part of the tag.