I strongly disagree. The main fuse has to blow when there is a short on the primary side, which clearly is the case here, else the PSU is a fire hazard if the automatic relay on the home's main electrical panel doesn't work as it should. The spark every time we connect the PSU to the mains means that high current passes through the circuit, however the fuse still remains intact. Another clue here is that our lab's relay on the electrical panel automatically dropped (saving the day), meaning that more than 15 Amps of current were drawn from this particular AC socket!! So clearly the PSU's fuse should have blown. Finally, I have seen a great number of blown PSUs so far and all have some common component failures: primary or APFC FETs, bridge rectifier(s), main fuse. In any case the main fuse has to go else the design has a serious flaw.
Some FETs might have increased Amps on papers, however in real life things can be different especially when the high RDS (on) values increase the operating temperatures. The part though in this PSU which I am not so sure about is the bridge rectifier, since it can only handle 8 Amps at 100C and usually I see more than 100C at the bridge. So if the bridge goes up to 115-120C its max current drops close to 5A according to its spec sheet so we only have 575W handling, which is much below the 700-720W that the PSU draws from the wall with 580W load.
The APFC choke isn't for filtering purposes, but mainly for boosting voltage, this is why it is also called boost inductor. More about how the APFC converter works and an explanation on both most popular types (DCM, CCM) can be found here: http://www.tomshardware.com/reviews/power-supplies-101,4193-10.html. I think it is pointless to explain APFC's operation here since there is an entire section about it. The bulk cap's charge didn't exactly blow the FET, the FET just couldn't handle the increased Amperage that the cap provided because of the high load. Also the bulk cap drew this load from the mains network and didn't make it out of thin air!
Finally please don't lose sight of the forest for the trees and confuse the readers on a subject that is clear. The fuse that protects the socket into which the PSU was connected dropped, meaning that more than 15 Amps passed through it! Given that this PSU's bridge can only handle up to 8 Amps normally its fuse should be less than 8A, however it survived not once, but both times that we tried it! This clearly shows a major flaw and on the same times proves that there is a short on the PSU's primary side, which draws LOTS of current! In any case the main fuse should open the circuit in order to protect the user and the equipment from damage or even fire. The main fuse not blowing is anything else but normal! I just have to point this out