When you have not enough VESTS, you can't vote.
When you have no VESTS, you do nothing. Yes, nothing, can't post, can't transfer..
The number of vest needed to participate is ridiculously small, the free steem power when you register covers it anyway.
Basic or derived data it doesn't matter, if the data is correct then it means that my steem power will keep growing while my vest will keep decreasing which means I will have unlimited steem power. I did the math with the data I was given from the site. Someone who have 1700 steem power will earn 70 steem power every week and will be able to cash out 16 steem power per week so it means that even when cashing out every week the steem power will grow.
If the data provided by steemit.com is false and that I actually have a lot less steem power than my wallet displays then it is a totally different story but i doubt it very much since nobody is complaining about it.
I'm telling you the math..
If you're powering down, every week the same amount of VESTS are converted into STEEM for you. You'll be left with less VESTS although it probably "worth" more STEEM (shows as SP). You won't have unlimited steem power, since there is a turning point.
When you started powering down, you get MORE liquid steem every week. For example, if you have 10400 STEEM worth of SP at first (which is actually X amount of VESTS but the exact X doesn't matter), now you started powering down. To be simple, assume the conversion rate increases by 3% every week (actually current value is about 4%, but the speed of increment is slowing down day by day, the final speed at equilibrium is about 0.7%)
(10400/104)*(1+3%)=103
STEEM out, leave10400*(1+3%) - (10400/104)*(1+3%) = 10400 * (104-1)/104 * (1+3%) = 10609
STEEM worth of SP in your account(10400/104) * (1+3%)^2 == (10609/103)*103%=106.09
STEEM out, leave10400 * (104-2)/104 * (1+3%)^2 = 10,821.18
STEEM worth of SP(10400/104) * (1+3%)^3 = 109.273
STEEM out, leave10400 * (104-3)/104 * (1+3%) ^3 = 11036.543
STEEM worth of SP(10400/104) * (1+3%)^4 = 112.551
STEEM out, leave10400 * (104-4)/104 * (1+3%) ^4 = 11255.088
STEEM worth of SP...
(10400/104) * (1+3%)^50 = 438.391
STEEM out, leave10400 * (104-50)/104 * (1+3%) ^50 = 23673.093
STEEM worth of SP...
(10400/104) * (1+3%)^100 = 1921.863
STEEM out, leave10400 * (104-100)/104 * (1+3%) ^100 = 7687.453
STEEM worth of SP...
(10400/104) * (1+3%)^104 = 2163.074
STEEM out, leave10400 * (104-104)/104 * (1+3%) ^100 = 0
STEEM worth of SP in your account. But if you didn't set withdraw route in advance, you can't even transfer the 2163 STEEM to another account. However you can stop/cancel the powering down at any time before your VESTS hit zero, but after that when you restart powering down, it need another 104 weeks to complete, which means you'll get out less STEEM every week (in comparison to the number before stopped powering down).In regards to this:
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.