The younger Teens Vs Facebook Traffic

I never knew Facebook is loosing the traffic from the teens. So i did a little Google search and found a similar article here in this link 
http://istrategylabs.com/2014/01/3-million-teens-leave-facebook-in-3-years-the-2014-facebook-demographic-report/

Comparing the difference of Teen Facebook users 2011 Vs 2014. The US population for teen are increasing but the Facebook users are going down.
So are they going towards more on Vine, instagram and other more visual sharing apps and social media sites ?

I found this another infogram in this Forbes link :
http://www.forbes.com/sites/parmyolson/2013/11/12/heres-where-teens-are-going-instead-of-facebook/

wechat,vine, snapchat are growing in a faster pace than the Facebook and other traditional social media sites (Facebook and twitter became traditional already in a decade - A very phenomenal growth in the internet).

So My question is How much should Facebook concentrate on developing countries vs developed countries ? In developing countries if Facebook lead with similar visual sharing apps, they could stay ahead in the game and I think they might not loose the traffic like they did in US.
Why is the younger teen's preferences changes so fast ?? or can you say a little about the brand loyalty among the younger teens ? and how to develop brand loyalty by an existing traditional company ?

Amazon Vs Brick and mortar stores - Millennials

Millennial being the future consumers of retail marketing. 
There will be additional costs linked to making these developments in the brick and mortar shop. This will impact the price of the product. One of the biggest advantage of online shopping is it less expensive and I don't need to drive to the store.

In the price stand point, Lets say if the brick and mortar stores makes small mobile shops (Brick and mortar shop) that holds samples of the products and a touch screen display that will let the customer check the online reviews and even could order it there with the online price equivalent to the amazon. Then the shop could ship the product to the customer just like amazon. 
Advantages of this option are : 
1. The overhead cost of big store could be minimized.
2. The order for the product can be made using a POS, so there wont be any need for typing the credit card information.
3. The customer can touch and feel the sample of the product before buying it.
4. The mobile shop can have a return stall, where the customer can return the product and request a replacement. Which is a big problem in Amazon. (Customer has to print a label, pack and ship it back - Then wait for the replacement). This can be overcome by using a return stall in the small shop.
Of course this wont work for all types of products.
My Question is how much millennial care about the difference in online pricing vs brick and mortar shop pricing ?(Now retailers like best buy are trying to equal their prices with the amazon).
Will the millennial go through the hassle of going to the store to buy the product ? when they have an easy option to do it online ?
How does their preference in shopping changes when they get old ? like when they have a family.

Mobile vs tablet vs laptop vs TV - varying Attention levels and level of annoyance

Is the only difference here are the screen size ? I always wonder if we watch a same content on all these 4 mediums, will our attention level differ ?

Case 1: brand Loyal content
I love walking dead, so lets say I watch the next new episodes in these 4 mediums, my attention level is gonna be the same. This is because I am loyal to the walking dead show. I dont care where I am or how I watch it. I am going to equally enjoy it.

Case 2: a new content but I choose to watch it :
all 4 mediums my attention level may not differ, since I choose this content.

Case 3: a new random content but it is intruiging :
Maybe my attention level varies, I get interested in the content better when I am watching it in my Laptop.

Case 4: a new random content, i am viewing for the first time (Like a Utube ad)
My attention level will differ. my guess.

Case 5 : same content, that I was exposed to more than 10 times.
My attention level will be same or minimal, but the level at which I am annoyed for watching the same content will it change with the 4 mediums ?

Cant help but wonder. May be I could scan or do a survey and see the results.

Numbers and metrics - Can you quantify how happy or sad you are by number ?

Math and numbers are the universal language for humans. Everyone understands it, everywhere we use it starting from music to probability of death by killer sharks.
With the social media like facebook, twitter, instagram. The importance of this metrics have evolved. The pressure to share posts and pictures that will get us maximum likes and retweets. Even though I myself hate admitting that I would be happy when I get more likes for my picture but it does not mean anything.
Why does it makes us happy when we get more likes for our picture. When checking a facebook friend's picture, our eyes automatically gets dragged to see how many likes and comments that person's picture has got. It is like highschool all over again except, now there is no age restriction to feel bad for yourself in facebook.
Now my question is why does this number of likes matters to us ? do we benefit from this in anyway ? why are we so emotionally connected to this number, even when I am in my mid 20's ?
So if we do quantify happiness and a mood of a facebook user via algorithms, will it be real or true ?
Will this trend change ? does facebook likes happiness = your saving in bank happy ?