a few things:

- a silly "me to" regarding "error_status":403,"error_string":"unwanted input",
   this time triggered by
    curl --dump-header - https://frisbee-bamberg.pbwiki.com/api_v2/ -Fop=AddUser -Fpassword=heinis -F_type=jsontext -Fadmin_key=XXXXXXXXX -Fperm=write -Femail=YYYYY@XXX

   results in

HTTP/1.1 200 OK
Date: Thu, 26 Mar 2009 20:13:28 GMT
Server: Apache
Vary: Accept-Encoding,Use
Set-Cookie: pbj=2860c530b67998d1721534aeabc3001238098408; expires=Fri, 01-Jan-2038 00:00:00 GMT; path=/; domain=.pbwiki.com
Connection: close
Transfer-Encoding: chunked
Content-Type: text/plain;charset=utf-8

/*-secure-
{"_request_id":"21.16559092205562061906.0","_valid_as_of":1238098408,"error _status":403,"error_string":"unwanted input 'admin_key'","reference":"http:\/\/frisbee-bamberg.pbwiki.com\/api_v2\/#Add User"}
*/

- can I actually use this api_v2 call to allow a user if the user
  previously asked for access and I got the email notification?

- not exactly belonging here but the web interface for allowing users via
  https://frisbee-bamberg.pbwiki.com/settings/users
  never worked for me. Everything is displayed, I enter email or if the
  user previously asked for an account I see the choice to allow or reject
  the user.
  Hitting accept does absolutely nothing for me. This is Ubuntu 8.04 with
  Firefox, Noscript and a few filtering proxies. However neither Noscript
  nor the filtering proxies display any blocekd connections so I am not sure
  where to start debugging?