I sometimes joke saying that I don't trust software I write myself. Sometimes I can take it further and say I also don't trust hardware I didn't build myself. But there is some degree of truth to it as well. It should take a lot of trust to use equipment that you don't fully understand the inner workings of. Being able to read the source may help, but soure code written by others can some times be hard to understand fully (depending on language and coding style).
Also, both software and hardware security has been hot issues as nations are suspecting hw/sw from other nations could be doing things they are not designed for. This is the topic of episode 94 of the Virtulization Security Roundtable.
