Well, the daisy chain cable can power 8 total ( NS-2 + 7 additional ). I guess one could tap in and add more "nodes" and still get power - it's not like the juice is firewalled @ 8, but I'd use that as the spec.
It really depends on the power supply. The NS-2 is just a distributor. If you use a normal Boss PSA adapter you will be able to supply pedals with up to 200mA. This means about 50 DS-1s or 1 1/2 RV-2.