Let me share my thought on this one. I simply thinking that this whole scandal is fabricated or even scripted. The media tend to lead us to believe what's fact they are represent, and us reader tend to fail to analyze the whole thing because our mindset "it's true when they told it's true" why don't we think "we want to believe it, but we may be wrong" and see the news from different perspective. That's why I found the scandal "weird" why?

1. so it's paparazzi photo, why it has different angle almost perfect angle and even good lighting? as you can see clearly their face inside the car. should the window tinted? why they turn on the light? so the photo can come out clear.
2. they don't even use disguise. no masker, no hat, nothing. Look at Yoona and Sooyoung case, they cover up themselves as if they don't want to be found out.
3. holy shat! Taeyeon even glance at the camera! what the hell? and they took it from up-front car. did the paparazzi climb a tree? Did they already set-up the paparazzi to have a good angle? or they even use hover camera to follow them from up angle?
4. This is the most bull scandal I ever seen. Why they open the rooftop? If they don't want to be found out, why doing the most stupid thing like that? as if they want the whole world to know. and I never found any scandal photo to be this "bold". And don't give me that crap they want to "annouce" their relationship. Taeyeon ain't that stupid.
5. It's maybe just a cover up or to make a sensation to create smoked screen in order to hide the BIG PICTURE.
6. SM stock increases after the scandal. It's entertainment industry come on! You will do everything to create profit. It's all about business and marketing. why I said it tho, EXO recently has lawsuit problem regarding Kris. and TTS will comeback soon. Entertainment business is really hard in Korea, and also the CEO himself has told that SNSD wouldn't last long. 
7. It maybe Marketing Cannibalism, lets see who got the most attention, EXO or SNSD. it's like taste the water, at the end the company will get all the profit. 
8. Why all this scandal happened in the same year, come on it's been like what? 6 scandals? please, it's just a strategy. see after this scandals will fans will stay support or leave. it can be as a way to get rid of SNSD's popularity little by little. Maybe the company thinks it's time for newcomer to shine.
9. Before this, SM caught on tax-fraud. it's pretty serious, even SM deny it but there's possiblity that all of this scandal released just to cover up? Korean Times even coverage this news.
10. Please remember, SNSD are SM workers. They follow what the boss says. 
11. there will be more scandal, and I predict next year maybe SNSD will have a long hiatus. 
12. Super weird when SM always confirms the scandal right away. 
my conclusion: It's all about business and profit.

So this is my thought from different point of view. I don't want to be naive. I'm a fans, but I want to analyze and I don't want to believe what media says without gathering other information. I love Taeyeon, yes I want her to be happy. But still she's SM worker, she has contract with the company. It's the risk of being idol, losing fans is one them. And she can't control the fans, she knows that's why she's apologizing. Maybe it's not her intention, maybe she were told to do so by company. Cruel life of being an idol. It's the most logical thought based on business' point of view.