The frustration of time-travel

It just occurred to me that the most frustrating thing about time-travel for anyone post-Intellectual-Property law would be the discovery of various things they themselves had previously identified as “wouldn’t-it-be-great-if” concepts. Case in point, Caller-ID: “Wouldn’t it be great if you could tell who was calling before answering?” Yes, it is. Everyone with a mobile (pretty much) has this. Imagine if you’d thought of it a little more seriously when you lived just a short while after Bell/Meucci/Reis invented/stole/plagiarised the telephone.