After 100+ Bounty Hunting missions (this is not a fabrication, I have each of them accounted for) I must tell you this: I've only not let my targets know I was after them twice in all these missions. Both sucked hard. I can't have fun myself if I don't provide a reasonable fun environment to the other guy. I'm not in Disco to "pwn" people. I'm here to play with people.
I remember this one time I went to Gamma after a Vega[TBH]. When I got there, he was just floating in space. I came by, prodded him (taunted him and fired one salvo against his ship) and noticed he didn't move or respond. Then I decided to PM him and say, "// Hey, Vega. Let me know when you are back. I'm waiting." Then I started circling around to wait him get back. Meanwhile, a Corsair Cruiser approached and started firing. I had to fly circles to avoid the Cruiser before Vega finally woke up so I could fight him. In the end I managed the kill and got to escape the Cruiser.
Now, there's a huge difference between announcing an attack and giving specific details about a job. I particularly like to play Mercenary because it allows me much more laid back cheesy punchlines if I'm feeling like it:
"Look! There's a flying paycheck. Here, boy, I need to cash you pronto." or
"Today I will make your wife a widow." or
"Whatever have you done to <clientname> to get him/her so angry at you?"
Which brings me to another point. Some clients DO ask to be identified to the target. You have to understand that this business is not about being successful in fighting. It's about understanding people. Normally your client will look for you, not so you can swiftly and efficiently eliminate their disaffections, they are generally looking for payback. Sometimes people come to us saying things in the lines of, "I want you to make this guy suffer. And when you've beaten him up good, then say, "<clientname> says hi."" Bounties from private parties are about payback.
As I write this, I've just sent evidence of a job the client specifically requested that we said, "Greetings from, <clientname>." If I didn't get the screenshot from me saying that before killing the guy, I wouldn't get paid.