Besides number of daily transactions hasn't increased from too much from last years , just with 15% in average.
That would mean that in the last year we had just a 16-20% increase in bitcoin users?
2) Why can't they?
They can try but because Quark devs implemented an automatic checkpoint system it verifies for double spend attacks and if one is found then some measures are applied, I don't know the technicalities because its sort of firewall so if we know how it works we can make an workaround, but most likely that bad node gets banned(read moer about banscore and bantime) and/or the block gets orphaned. The trusted node on which the checkpoints are being verified is in Max's control but I don't know exactly what measures are applied but basically Quark is protected against double spends even with a low hashrate. I have tried studying the tcp traffic and its very interesting how it works, with every node our Quark client connects we exchange info about the past checkpoints but because its binary I wasn't able to see exactly whats going on.
So basically you don't rally know how it works but you are sure that it will work.
To me that would mean to be over confident of something that might make me lose money.. err had made me lose money.
Let's say that this "banning" of a "node" lols , can't help the laugh , works.
Again , how many i5 cores do i need at the current rate to keep the blocks empty and deny any transactions?
You know how your firewall works in technical details ? As for banscore and banned nodes, these are actual working verifiable features in the source code.
I don't know how many i5/7 you need, why don't you mine and tell us ? What will you obtain ? Eventually you'll be better off just getting the quarks, if you have more than 50% you'll get 500K in 1 year