So, I can invite a popular friend and give him 10 invites, and I can invite my other friend and give him 1 invite.
Even giving everyone 1 invite every day would be better.
No, no, no. This is the problem I have with Diaspora. They gave me 5 invites. I used my first since I got mine as part of an invite chain. I have no clue how to best utilise the other four so as to maximise the usefulness of Diaspora (i.e. grow my own social network maximally). End result, I haven't used any of my other 4 invites due to analysis paralysis and my social network is basically dead.
Google+ seems to be off to a pretty good start so far. I'm not exactly sure how the invite structure works, but somehow a significant portion of my social network seems to already be involved. I'm assuming this just means I know a lot of connected people (most of my network is from college and we all know people who do or have worked at Google), but it means that, even within the first 24 hours, activity has been pretty decent.