In regards to this:
The number of vest needed to participate is ridiculously small, the free steem power when you register covers it anyway.
Currently, if you have only 3.5 SP, you can vote a few times a day. If you have more you can vote more times. So for tiny accounts, it's able to participate, but the level of participation is limited.
And, if you've read the whitepaper, you'll know there is another bandwidth limit designed in the system which will only show when the system is getting much more busy than present, however I don't think we'll reach that limit in the near future, so we can just ignore it for now.