Thanks for the link. But that only reduces the variance, it doesn't increase the expected gains from forging. Pools "work" (well, used to work) for Bitcoin and friends because expected gains (used to be) > costs even for small-timers, but the variance was extremely high. Nxt has low expected gains from forging. Poor shibes like me will likely have have expected gains of < 0 (after electricity and hardware costs), the only profitable ones may be ones that can do it in scale and have market advantages in the different parts of the cost equation, to keep costs down.
I share the concerns of centralization, but seems to me the way to deal with that is for leasers to be able to have some kind of influence on the forger's behavour (i.e. what txes they reject, scripts they don't run and how they blacklist/weigh other forgers). Maybe moving leasing power to someone else is sufficient, or maybe there needs to be some way for leaser's to inflict a penalty (but maybe with their own reputations on the line).
Expected gains = rewards - running costs
Running costs are extremely low for NXT: As most users have flatrates, it basically comes down to power costs. Even running the forging client on a netbook would only cost about 25 per year. Using the average per day there are
3.347.046,35 NXT fee generated per year.
This means, that forging on a netbook at the moment is profitable if you have more than 173,704.0 NXT on your account. As the price will increase and it is always possible to reduce power consumption by using a rasp-pi and a solar-panel, i do not think, that expected gains is a good argument for pooled forging.
All you could save by pooling would be 173,704.0 Nxt at the moment - a lot less if price increases.
Edit: Math was a off