There is absolutely no truth in being "marked" in the practical sense.
How can the govt go around marking nearly 40% of the population? And what can they do with these people? Chase them out of HDB flats, confiscate their CPFs? Deny them their edusave and growth dividends, etc?
In theory, the govt can trace your vote because of the serial numbers but then again this is disputable because the vote boxes are sealed in the presence of opposition members and destroyed also in the presence of opposition members.
Of course there will be some skeptics that will claim that the govt can go thro' the votes while they are in storage and "fixed" backed the seal, etc.
Personally I doubt it. History has proven that these opposition supporters do not go round creating trouble. Do we take to the streets for the slightest issue?
However, when the govt introduce the serial number on the ballot slip, Prof Tommy Koh (then Dean of Law Faculty, NUS) objected and raised the issue that the numbering instill a certain fear in the people. This is true to this day (hence this thread!). For that Prof Koh was sidelined and removed from his position and has now been "re-engaged" by the govt. The govt took advantage of this fear and operated within this environment of fear to their advantage. It is like I am telling you there is no ghost and scientifically proven so, but would you still be scared when walking in the dark?
Govt will target prominent people who step out into opposition politics. Who and what makes you prominent?
As an opposition, if you engage in issues, the govt deem you harmless. Example, LTK, Slyvia Lim. But if your strategy is to discredit the govt thro' some info that you have or know , then they "marked" you. Example Francis Seow.
If you are brave and dare to challenge the govt, then you would also fall into this category. Example, Tang Liang Hong, CSJ, Chia Thye Poh.
I have voted for opposition since the day I could get hold of the ballot slips. I make it known I cannot be in the presence of MIW and have no wish to be associated with them. I have no problems walking the streets of Singapore and have not been denied any rights due to me as a citizen. In fact, I speak openly for or against the govt if the need be which is more often against.
Let not this fear gripped you, The govt has more fears that their current PAP members jump ship to the opposition (which has happen before). This is more damaging than outsiders criticising the govt. Internal dissension is more damaging. Notice how quickly ex MPs like Tan Soo Khoon, Tan Cheng Bock, etc, are all but shreds of memories.
Now you understand why the govt look after their own, so that even if they retire from party life, they continue to be financially well fed into their golden years with all kinds of directorships. The best way to keep the mouth shut is to sealed it with a dollar bill. The bigger the denomination, the louder the silence.