Oh you piece of gold!
Finally someone giving some insight into this enigma!
And even a super moderator, which means that you know what you're talking about!
Thanks! Might help dozens and dozens of people always asking the same question.

Well I was about to think that it must have been some intentional limitation.
Unfortunately now, the 'Add' button is indeed worthless!
You can add and add, but the host will always disappear as Bailit said! So better just remove it entirely, as you will anyway be reconnected if you remove one of the hosts.

Well ... you're saying "banned by some p2p apps"?
OK, but it might be that way, I can get more search results from Limewire users which I otherwise would never be able to spot!
So it might be a good idea to have an older version of LW handy to get more hosts! I will try this!! *DROOOOL*

Lastly ... about the statistics...

I can see "Hosts : 133" now.
Is this REALLY ONLY 133 machines connected to this network or am I asking a kind of naïve question?