I keep all my machines listed on the IPDB serial number database because I like to
a) keep the numbers up to date for other collectors on that data base
b) keep every detail logged somewhere for insurance claim details etc
c) but more importantly, if some mongrel breaks in and decides to steal any of my machines, if i saw any machines matching mine, being sold somewhere, i could play detective before breaking a few arms n legs.lol

I reckon the ipdb serial number database is excellent. well worth the effort.