Even if it is technically feasible to route traffic over a server,
A computer running Linux is not a server. If it's job is to route and forward packets, then it is a router. And the fact that people are pushing the envelope at 10G is because Linux routers are already known to do a great job at 1G and below.
It is not about making it work, it is about having it work -all the time-,
You can't buy "...having it work -all the time-". The only way to achieve that is by building in proper redundancy, probably N+2 or more, and by paying attention to all the deployment and operational nits that equipment vendors will not do for you. Companies like Google have demonstrated that this can be very effective with cheap components failing all the time.
even if it is more costly, even if YOU have failed troubleshooting a crash, SOMEONE will be forced to help you, by contract.
Contracts never force anyone to help you. They only force the vendor to pay a penalty when they fail to help you. When miracles are needed, you had better design it into the system yourself, not rely on a vendor to provide them.
Risk assessment folks, risk assessment...
Indeed! If you want to cover your behind, then buy the big brand names and forget about the consequences. If you want to operate a network service that functions all the time, then make sure you control and mitigate all the risk elements. Don't assume that a big brand name will do it for you. In particular, big brand names focus their effort on the majority customers so if you want to do something a little bit different, you will find that the big brand name won't be able to help you until next year, and that is assuming that their priorities don't shift your request right off the list. --Michael Dillon