At Page 1 of NEMTechnical Reference:
PoI is similar to Proof of Stake (PoS) except that it is not solely derived from the size of an account's balance.
The words "is similar to" hide POI innovation.
It's true though. PoI is a modification of PoS that takes factors other than just your staked coin balance into account. The number of changes to the standard PoS implementations probably warrants it being put in a separate category but the basic idea was still born out of PoS.
depressing when your importance slides
do exchanges build up a bs level of importance on the NEM network?
You don't need to be depressed.
In Poloniex's case, they use user's fund in harvesting less than 25%.
(More than 75% is stored in cold wallet, and do not harvest.)
This is less than ordinary nember's use of xem in harvesting.
Perhaps, ordinary nember's harvesting might become higher owing to their not-doing-harvesting-fund in coldwallet.
no exchange should be gaining POS coins from users funds
It's pretty typical for exchanges to stake with their customers' funds. I believe most (if not all) major exchanges do this with coins stored in their hot wallets in order to get some extra profits on the side.
You know, this whole issue wouldn't be as much of an issue if so many NEM holders - and crypto coin holders in general (this isn't unique to NEM) - weren't so quick to move their coins to exchanges to dump.
For a lot people here it really is all about getting BTC to get fiat and nothing more - crypto's only a means to an end (fiat). Any coin (included BTC) is just a temporary bus station to fiat. Let's face the fact that this is the mentality, which is why exchanges have so much market power over crypto prices, whether they stake or not.
A ridiculous percentage of NEM ended up right on Poloniex after the initial distribution - lots of people raced to dump. I think it also reflects the low level of trust in crypto - lots of people have little faith that any of these coins retain their value for long and, judging from what we've seen in crypto the past two years, who can blame them?
I don't blame them. Looking at the all time charts for most cryptos on Coinmarketcap.com, you'll see that most of them look very similar. What usually happens is that the price goes up initially once the coin hits an exchange. Then what follows afterwards is a steady decline that tapers off once the coin is made irrelevant. People have come to expect this pattern for every new coin that's released so it has morphed into a self-fulfilling prophecy. Sometimes you might see a random pump or two in the middle but afterwards, the price usually continues to decline as before.