botnets are a problem but it depends how many. If botnets only make up 5% of the network, then they are having small effect on the price - and the price is mostly being set by honest miners.

the same can be said for server administrators taking advantage of their networks, mining primecoin at zero expense. There is only a finite capacity of botnet miners and zero-expense miners. I think they can be overwhelmed in time by serious miners who set up professional cpu rigs - who then becomes the major determiners of the xpm price.

At this point I think at-home-miners are struggling to overtake the zero-expense miners. and probably will for some time, unless more investments are made into xpm mining.

and GPU mining is still a possible factor... which might make investment into cpu-rigs cautious.