I really want to take my SP out of the vault because I think having it on me in plain view will help motivate me to restock more in a weird way. :P I only get like 2.7k interest per day anyways.

But there're pet sites with random events that'll take a percentage of cash out of your hand. Does this game have any random events like that, or is it 100% safe?

Occasionally, you'll get taxed on your on-hand sP but I don't think that happens very often and it help you earn achievements anyway. I think that's about the problem RE...

Sebastian Phoenix will sometimes tax you a certain percentage of your on-hand sP (which, obviously, you get taxed more if you have more on-hand). I believe Maleria still has a random event that takes some sP, but I'm not sure how much she takes (whether it's always a small amount or if she takes more if you have more on-hand).

Depending on how much sP you have the tax can get pretty pricey. I was just taxed 35,000 sP tonight while I was doing saggitarius quests... I hadn't deposited my sP into the bank yet.

I would only keep out a portion and not everything, but that's just me. :)

I try to keep no more than 5-10 mil outside of the vault because of dear, sweet Sebby, as other people have mentioned. When I've had about 10 mil on hand he usually takes about 1 mil of it.

right now, the Achievements for being-taxed don't seem to be accruing. Taxation used to be very rare indeed, so rare that I used to keep nine digits "in my pocket" so I'd have any chance at all at the top tiers. Now it is more common, so I keep in the mid sixes when questing, less than that when restocking

I do a lot of restocking, and it's pretty rare to be able to spend more than two million per day, even on holidays when everyone's out summer picknicking...and IMO that's only if you only restock elixirs and jewelry which have a high wholesale value.