Have you ever asked how many contacts will you have on your roster in the future?
Propietary instant messaging services limit your buddy list to 150 or so.
Is there any limit in a Jabber roster?
Of course, public servers should put a limit to prevent buggy clients from compromising the server.
But how high is the technical limit? Maybe 500? 1000?
And what happens when you have so many contacts in your roster?
As far as I know, XMPP does not impose any limit, and there is no recomendation.
So servers and clients will tell what's the technical limit.