Might be an injoke coz the BBC sometimes actually do put out T-shirts with those lines on them. It might have a greater commercial significance than being purely plot-significant. More might become of this in Series 4 but until then, I will assume that it is said to keep fans guessing what merchandise they will release rather than it being a clue to something really important in the plot.

The BBC actually made those T-shirts, there is a little advert inside the S3 DVD about them,,, so perhaps it was a chance to sell merchendize? 

But maybe since there is a bit of 'connection' between Mary and Magnussen one of them picked that line up from the other? 
 

Tho series 3 may fit that even better!

IBelieveinSH wrote:

Sorry to dig up this old post - I'm new here - but I too was wondering about this coincidence. And we all know what Sherlock says about them.

Another thing that sticks out to me is when Sherlock contronts her - getting her to reveal her secret to John - and he says that he'll take the case, to which she responds....what case? Also, why in the world would she carry - on her person - a flashdrive with of her secrets on it?! I'm not sure if it was just in my head, but she seemed to stumble a bit when John asked her what AGRA was. Like the drive wasn't actually what she said it was, and knew she could guilt John into falling for the bluff. And yet another question....why would Magnusson target an assassin, knowing what she's capable of?

Yes, AGRA flashdrive could very well be a bluff - still, during Christmas, when John confronted Mary again and showed her the drive, she reacted very strongly, like as all was over with her.... so I´m not sure it really didn´t contain some data.

As for Magnussen, I believe he managed to be in his blackmailing bussiness for a long time, without anybody seriously opposing him, so he got too cocky and felt like he´s invincible.... so he lost his wariness around people like Mary and believed she too will yield to him in fear... and that was his big mistake."Hochmut kommst vor dem Fall" - or like they say in the biblical proverbs: "Pride goes before destruction and a haughty spirit before a fall".
 

Yeah, that quote applies quite well. And he absolutely misjudged Sherlock.

And I can also see how having it on her person would be safest....but why have it at all? Why did she also still have all her assassin gear if she truely left the business?

I understand that Magnusson was trying to get to Mary by attacking John and so happened to find that John was also a pressure point for Sherlock in that act. Obviously he has eyes and ears all over the city since the messages addressed Sherlock as they were on their way, plus the video footage. But I have to wonder if she worked for him (in the past) and refused to do something when approached, saying she left that life, thus provoking the attack. I mean most people later in life have coworkers as their closest friends, so it makes sense that Janine was her maid of honor and works for Magnusson.

I definitely like to think the best of Mary and that she actually does love John and is trying to escape an evil past. It would be way too sad to find that the whole thing has been a sham to get to Sherlock. I know they'd been together for at least 6 months before Sherlock announced himself alive to John, but like I said, Magnusson has eyes and ears everywhere. How else could he even know about Redbeard?

IBelieveinSH wrote:

Did anyone else catch this? I just did! I didn't realize Sherlock had deduced that Mary was a Liar right from the start!

Yeah, this is really fascinating! But do we exactly know what was Sherlock referring to? Maybe he only realized that something was wrong with her - well, but what was/is it at this very first deduction?