Mindark is a single company in a foreign country (for most of us). Companies can go out of business or change their practices with no warning. Mindark gives no guarantee that they will be in business when you go to withdraw* the money you deposited. Treat this like a high-risk investment. This means do not deposit money that you can't afford to lose.
Additionally, if you're investing to "play", then don't expect to get any significant withdrawal when you quit. This is a pay-to-play game, not a free-to-play one, and the system is designed so that you will lose money on every "fun" activity (hunting, mining, etc). You can make money by trading, and if you approach it as you would a business, you can make enough to fund your game play. I recommend that you thoroughly explore the game and the economy before depositing significant amount of money. The cases of people withdrawing thousands of dollars are mostly cases of where people deposited even more previously, so don't expect to deposit $1000 now, play (hunt, mine, craft), and in a year withdraw $1000.
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*The word withdraw seems to be misspelled very frequently on this forum. The verb is present withdraw; past withdrew; past participle withdrawn. The noun is withdrawal. Withdrawl is not a word.