Windows devs are often careless enough to compile stuff with hidden backdoors (at least I was until a few years ago), and using precompiled binaries as suggested invites that. However, just as the Windows Satoshi client has signatures from core devs, libbitcoin binaries could do the same thing, so it's a minor problem... at least if the signing developers have a reputation to protect.
My videos show how easy it is to build the four static libraries from source, for bitcoind (and other *coins). I actually built two of them in the videos and show how easy it is to build the other two.
Ron