I don't know why, but this operation has always really annoyed me. They don't do it very much, but why do it at all? I can't figure out the logic behind it. If anyone can shed some light on this, I'd love to hear a valid explanation. My thoughts (after the "read more"):
1) Congestion / confusion: South Station platforms are already incredibly crowded - especially at the foot of the platforms between the headhouse and the platforms. Adding this operation to the PM commute adds more congestion and crowding to the platforms. The added congestion can prevent a commuter from getting to their train on time. For example, if they are checking tickets on track 4 and a commuter is trying to get from the Atlantic Street entrance over to track 9 or something, that commuter may get caught in the crush of people waiting to have their ticket checked, even if the train on track 9 isn't affected by the checkpoint (and therefore not 'waiting' for the people to clear out of the checkpoint).
2) If you don't have a ticket and are willing to pay the surcharge (or are planning on buying a ticket on your phone on the train) are you prevented from boarding the train? Why? Maybe you're running late and you can get to the train and don't have time to buy a ticket prior to boarding. This is a legal, acceptable action - why is it prevented today on the trains being targeted? If someone running up to the train at the last moment is allowed past without showing a ticket, doesn't that defeat the whole checkpoint system?
3) If you have an e-ticket on your phone and have to activate it, how can you show it to the conductor later? And if they're not showing activated e-tickets at the 'checkpoint,' what is the point of showing anything? EDIT: As @tarynw512 correctly points out, e-tickets are good for an hour. So I'm wrong with this critique. I have only used the e-tickets a few times, and I should have done more research before making this comment.
4) What is the goal?
a) If the goal is to remind people that there is a surcharge for tickets bought on board, then just position some Keolis customer service agents at the foot of the platform announcing that.
b) If the goal is to 'catch' counterfeit tickets, then why not make it more random and more frequent? Give some conductors or customer service agents the 'purple flashlights' and have them ride a few trains. Send a Transit Police Officer along with them to deal with any issues. Sending out a prior announcement about checking tickets allows any intentional counterfeiters an opportunity to buy a legitimate ticket and avoid having their counterfeit tickets caught. They might catch someone who unknowingly has a counterfeit ticket, and I think this has actually happened in the past, but I think that happened on the subway. EDIT: It was on the commuter rail, but it was the sharp eyes of a conductor - not a useless blanket sweep system - that caught it. Details here.
5) Unfairness: Without this operation conducted at Back Bay or Yawkey, it seems to unfairly target / inconvenience South Station passengers. I'm not sure if they do it at Back Bay occasionally, so this criticism might not be as valid.
Again, if anyone can give me a reasonable and logical explanation of why this is a good idea, I'm all ears. But to me, the ends (which are unclear) don't justify the means. I'm all for preventing counterfeit tickets, but this doesn't seem to be a good method (if that is the intent).