Max MN = (total coinsupply)/ 2880.
A while ago I remember there being a discussion about limiting one MN to one IP (or server)... what's the latest on that?
You can't limit one SN to one IP.
Nobody can know if your server is really running on one IP as a single instance or running as one of hundred virtual machines in a cloud.
Also, your SN will never be required to be visible thru an IP, the SNs IP is not important since it's not broadcast anyway.
With that in mind, coming back to your question:
to prevent people from running multiple SNs (servicenodes) on a server, you will need to run services (on those servicenodes) that have a high load on the server CPU / RAM / HDisk...
this will make running multiple SNs on a server problematic, and encourage the spreading of SNs over multiple Servers (and be it only virtual ones)
For this to work we will need a sophisticated valuation system that gives the best servers the best score, and the worst servers the worst score.
That's the tricky part.
Or you could avoid all this pointless and impractical nonsense and just have a fixed collateral cost, and let market forces sort the numbers out. Spread MNs would be up and running on mainnet with IX far faster.
"Pointless and impractical nonsense" is not a valid counterargument.
If you need fixed collateral cost go to Darkcoin/Dash/whatever if will be called tomorrow.
Spreadcoin will go its unique way, following the principles of true decentralization, enabling competition and easy entry for everybody.
Stay tuned.