Aaronut nailed the answerAaronut nailed the answer. He's 100% correct. Now, for my 2 cents.
The three obvious problems are the shortening, the flavoring, and the meringue powder. That's obvious just looking at the recipe. Even Wilton agrees, amusingly (I'd cut out the vegetable shortening entirely.) This is more my style.
But you wouldn't need someone to tell you this if you tasted. For a no-cook item like icing, you need to TASTE the ingredients. Taste the flavoring. Stick your finger in it and lick it. Is it good? Does it have a weird chemical flavor? Taste the nasty nasty vegetable shortening (then throw it out the window. Yuck.) See how it's not as good as butter? Taste the meringue powder. Blech.
Every flavor you put in icing is going to shine through. I live in a humid area, so I constantly need to tinker with consistency, and that is impossible if you don't understand your flavors. Don't be afraid to taste it at every step of the process, and, if it tastes bad when you finish, throw it out and start over. Don't ruin good cake with mediocre icing.