I'd keep it handy. I'm terrified of the idea of killing people, but having that particular ace up my sleeve if I get into trouble? Literally up my sleeve, a little scrap of the paper? It's hard to imagine a specific act-or-die scenario where I can get my assailant's name, but, fuck, wouldn't my face be red if something like that happened and I didn't have the power?
Yeah, there'd be the temptation to use it on people I feel 'deserve it', and I don't know for sure I'd be able to overcome that- I'd like to think I would, but that's the problem with hypothetical abilities- But I'm not going to throw away the most powerful weapon on the planet just because I don't trust myself, and I'm certainly not giving it away.