Actually, I mused have screwed up last night. The version of curl I have does su...

Actually, I mused have screwed up last night. The version of curl I have does support it and does put it into the Auth header.

  % curl --trace-ascii /dev/stdout http://jimktrains:password@news.ycombinator.com
  == Info: About to connect() to news.ycombinator.com port 80 (#0)
  == Info:   Trying 184.172.10.74... == Info: connected
  == Info: Server auth using Basic with user 'jimktrains'
  => Send header, 223 bytes (0xdf)
  0000: GET / HTTP/1.1
  0010: Authorization: Basic amlta3RyYWluczpwYXNzd29yZA==
  .......

Some UAs however, do just drop it. Like IE (http://support.microsoft.com/kb/834489)