If you take writing seriously, odds are, people will look at you funny.
No, really. Beyond the whole, “What do you mean, you got up at 4 AM and it wasn’t to go fishing? I knew it! You’re seeing someone else! How long has this been going on?!?”
Which, if you’re an honest writer, is going to be hard to answer both accurately and politely. Because you are “seeing” someone else; likely quite a few someone elses. The fact that they’re completely fictional may cut no ice whatsoever.
Assuming you manage to negotiate that conversation without either A) breaking up or B) your significant other committing you for psychiatric observation, then you have the broader real-world hazards to deal with. Such as your internet search history.
If you write action at all, you’re going to have a very… interesting… search history.
What do different guns look like? What happens when a car/plane/ship blows up? Where are people likely to have an “accident?” What are the symptoms of disease X, poison Y, injury Z?
Your search history, to be blunt, is going to look like you’re plotting something horrible to do to somebody.
Which, again, you are. Just, a fictional somebody. Hopefully the FBI will understand.
(I have visions of some newbie agent charging into a room with, “I’ve got a live one!” And the rest of the squad looking at what he’s pulled up from someone’s search history. “Poison, how fast a body decomposes, fastest way to kill someone… bronze age metalsmithing?”
Older agent: “Wait. What month is it?”
*Checks the calendar. Groans.*
“Probie, we need to talk. See, every November, there’s this thing called NaNo….”)
For a real life example of this, look up Tom Clancy. Apparently after he published The Hunt for Red October he had a lot of conversations that went something like this:
Government Agent: “Who told you about this?”
Clancy: “Told me about what?”
Agent: (Beat.) “…We can’t tell you, it’s classified.”
Though if you do write and publish, the FBI may be the least of your worries. Make even one penny from your writing, you count as self-employed. Be very, very sure you get all the 1040 paperwork and (multiple!) associated forms right. The IRS has no sense of humor.
Last but certainly not least, there’s the danger of being a writer out and about in the environment, especially when you have a little time on your hands to start picturing how characters might interact with the spot you’re standing in, and why they might be there. For example, there’s one particular spot of live oak scrub with greenbriar and saw palmetto underbrush I know of that you would think was very public. It’s between a highway, a mechanic’s shop, and a dentist and separate other medical complex. But if you actually walk the edge of it… get a foot or so in, no one can see you. The noise from various pneumatic drills and the highway would cover any small sounds. You can back right up to the underbrush if you pick your spot right. And given the nature of the various businesses around it, they’re closed after sunset… and while there are security lights and may be some cameras, they’d all be focused on the businesses themselves to catch break-ins. Not the edge of the parking lot.
If you write mysteries, or even read mysteries, you can already guess what potential a bad guy might see here.
Fortunately nobody was around watching me pace out the area and scribble notes. It might have been hard to explain!