2Thes 2:3; Let no one in any way deceive you, for it will not come unless the apostasy comes first, and the man of lawlessness is revealed, the son of destruction,
2Thes 2:4; who opposes and exalts himself above every so-called god or object of worship, so that he takes his seat in the temple of God, displaying himself as being God.
2Thes 2:5; Do you not remember that while I was still with you, I was telling you these things?
2Thes 2:6; And you know what restrains him now, so that in his time he will be revealed.
2Thes 2:7; For the mystery of lawlessness is already at work; only he who now restrains will do so until he is taken out of the way.
2Thes 2:8; Then that lawless one will be revealed whom the Lord will slay with the breath of His mouth and bring to an end by the appearance of His coming;

Apparently the "man of lawlessness" (the Beast) will be revealed at some point before this. Both verse 3 and verse 8 above say the "lawless one will be revealed".
So I don't believe anyone will take the mark by accident. There may be some who take it because of ignorance. But I believe everyone will know who/what the beast is.

.. to be continued ...

The Bible does mention another mark of a different type on people's foreheads in Revelation.

Rev 7:3; saying, “Do not harm the earth or the sea or the trees until we have sealed the bond-servants of our God on their foreheads.”
Rev 7:4; And I heard the number of those who were sealed, one hundred and forty-four thousand sealed from every tribe of the sons of Israel:

So it seems at least 144,000 will receive a mark of God on their foreheads.

Rev 9:3; Then out of the smoke came locusts upon the earth, and power was given them, as the scorpions of the earth have power.
Rev 9:4; They were told not to hurt the grass of the earth, nor any green thing, nor any tree, but only the men who do not have the seal of God on their foreheads.
Rev 9:5; And they were not permitted to kill anyone, but to torment for five months; and their torment was like the torment of a scorpion when it stings a man.

Now it seems that if you have this mark... most of the plagues on the tribulation won't affect you. You will be protected by this mark. ( also see Rev 14:1; and Rev 22:4; )

However if you have the mark of the beast... it seems just the opposite will be true.

Rev 16:2; So the first angel went and poured out his bowl on the earth; and it became a loathsome and malignant sore on the people who had the mark of the beast and who worshiped his image.

.. to be continued ...

2Thes 2:8; Then that lawless one will be revealed whom the Lord will slay with the breath of His mouth and bring to an end by the appearance of His coming;
2Thes 2:9; that is, the one whose coming is in accord with the activity of Satan, with all power and signs and false wonders,
2Thes 2:10; and with all the deception of wickedness for those who perish, because they did not receive the love of the truth so as to be saved.
2Thes 2:11; For this reason God will send upon them a deluding influence so that they will believe what is false,
2Thes 2:12; in order that they all may be judged who did not believe the truth, but took pleasure in wickedness.

One of the more frightening passages in the Bible. Not because it's about the beast, but because people that didn't "receive the love of the truth so as to be saved" will be deceived.
If that isn't bad enough, God Himself will send a "deluding influence" upon them "so they will believe what is false".

What a sad state to be in. You have rejected God and the truth of salvation for so long.... in the end God just gives you over to what you want to believe.
He is going to make sure you don't change your mind in the future. The Bible actually mentions God doing this a number of other places in the Bible.
(Romans 1, 1Cor 5, Pharaoh in Exodus, etc..) It seems once you take the mark.. there is no redemption. You are doomed. You will be unable to repent.

The penalty for taking the mark is about as severe as it gets.

Rev 14:9; Then another angel, a third one, followed them, saying with a loud voice, “If anyone worships the beast and his image, and receives a mark on his forehead or on his hand,
Rev 14:10; he also will drink of the wine of the wrath of God, which is mixed in full strength in the cup of His anger; and he will be tormented with fire and brimstone in the presence of the holy angels and in the presence of the Lamb.
Rev 14:11; And the smoke of their torment goes up forever and ever; they have no rest day and night, those who worship the beast and his image, and whoever receives the mark of his name.”
Rev 14:12; Here is the perseverance of the saints who keep the commandments of God and their faith in Jesus.

John expressly says here... they will be tormented with fire and brimstone, the smoke of their torment goes up "forever and ever". (forever is a long time).
He also implicitly states... "the saints who keep the commandments of God and their faith in Jesus". Are the ones spared from this punishment.

I have to say... I wonder sometimes if some people have already reached this point... they believe things that don't make sense, they do things that don't help their cause, they do things that directly go against humane decency of humanity.
I wonder if God has already sent a "strong delusion" upon some people.