What would happen if all 7.8 billion People screamed at Once, in One Voice using
the word "" I Loveeeeeeeeeeeeeee Youuuuuuuuuuuuuuuuuuu""

Nothing unless they were also feeling that deep unconditional love.

It has been researched even to send love to DNA, many people doing this at the same time for a length of time, all trained in meditating, generating love etc.
Result: nothing
They had another large group THINK of the DNA, to uncurl.
Result: nothing

Then they had a large group THINK and see the DNA uncurling and at the same time sending love.
Result: DNA moved!

Meaning... love alone does nothing. Thought & intent (affirmations!) alone do nothing.
But combined... THEN you got power in your hands!

So everyone shouting "I love you" won't do anything much unless everyone actually feels that high vibe of love AND it's combined with intent.

I'd have 7.8 billion less friends.

And a huge headache!

However, considering the world saying the words 'I love you' in different languages would be irritating in certain places.
Plus, due to areas which are very sparsley populated, you would only actually hear yourself.
Here in the states there are many different cultures living in close proximity to each other in cities.
It would be irritating to hear so many languages being screamed at the same time.

For example:
English - I Love You.
French — Je t'aime.
Spanish — Te quiero.
German — Ich liebe dich.
Croatian — Volim te.
Italian — Ti amo.
Portuguese — Eu te amo.
Swedish — Jag älskar dig.
Romanian — Te iubesc.

On a side note; This is a thread I would expect from children in an elemetary school. Something a 5th grader would think about. I find it fascinating such a subject would show up in an adult dating site's forum.

Peculiar statement. I actually found it quite deep. I guess it depends on how you interpret it.
The way I do, it requires knowledge of certain science and Law of Attraction. Most adults don't even have that.

Okay...
Perhaps its the What would happen if all 7.8 billion People part of the OP. "What would happen" were types of questions we would have in 5th grade. What if...? was a common idle chat topic all thru school and college.
Sometimes the topic of the querry would be something very interesting which applied to our actual life conditions and sometimes they would be topics which would be impossible at that time or ever.
What if, is the premise of science fiction and fantasies. What if, is the premise of horror and action stories. What if, What would happen if, are pre-claimers to unlikely conditions. Usually not taken as direct possibilities, at least in idle conversation.

I remember a short conversation in 5th grade... What would happen if everything alive in the world farted at the same time? We had a lot of fun laughing and giggling at what we all came up with. We did a whole range of bunny fart jokes and moose fart jokes and combinational jokes and drew pictures and made fun of people as to which animal their farts would resemble. Children's mentality.

screamed at Once, in One Voice using
the word "" I Loveeeeeeeeeeeeeee Youuuuuuuuuuuuuuuuuuu""
Is the focus of the what if scenario.
Its playful in how its presented.
It, to me, doesn't involve the moral implications of world love.
It doesn't even have the same intent as when the world tried to sing that song years ago. (I heard nothing) I forget which song was sung.

The Voyager Golden Record has a greeting to aliens from the people of the world. You can hear the different languages as spoken in natural dialects.
You can read (in English) what was said.
http://voyager.jpl.nasa.gov/golden-record/whats-on-the-record/greetings/
If all those languages were to happen all at once around the world at the same time as loud as possible it would be ... noise.

What would actually happen is very different that the fantasy expectation of what would happen. Remembering that the world has different time zones as well means some populations would be screaming at 3 am!

Now, when I love someone with everything I am, I have no problem screaming it from the rooftops. I'd write it in the stars if I could. When I was little, dad taught me how to yodel. I've yodeled my proclamation of love over a valley before. That was VERY different than everyone in the world screaming I Love YOU at the same time.

This is just a Thread, so for me both Positive and Negative Comments are Highly Appreciated .
I AM USED TO IT !

If that really happend, then the majority of those people would be lying

Two answers:

1) "I'd like to teach the world to STFU!"

2) "Good morning. In less than an hour aircraft from here will join others from around the world and you will be launching the largest aerial battle in the history of mankind...
Mankind, that word should have new meaning for all of us today. We can’t be consumed by our petty differences anymore. We will be united in our common interests. Perhaps it’s fate that today is the 4th of July and you will once again be fighting for our freedom not from tyranny, oppression, or persecution but from annihilation. We’re fighting for our right to live, to exist, and should we win today the 4th of July will no longer be known as an American holiday but is the day when the world declared in one voice, “We will not go quietly into the night. We will not vanish without a fight!!. We’re going to live on. We’re going to survive. Today we celebrate our Independence Day!”

The decibel level would be too much for my dainty ears!