Balloons are a metaphor for disappointment.
Shiny on the outside... but empty inside.
You must also live with the knowledge that you will either lose them and they will float away... or you will hold onto them and they will slowly deflate and sink to the ground.
But they're great to f*ck.
Balloons can go places that human beings cannot go without help from technology. I see the balloons' existence as a metaphor for humanity's dreams taking flight!