http://www.techwench.com/the-drawbacks-of-using-a-telescopic-zoom-lens-in-digicams-a-user-guide/

In comparison to a prime lens, a telescopic zoom lens provides an image of much lower resolution. The introduction of zoom lenses afforded both photographers and filmmakers a cost efficient way of producing shots with different compositions. There are many advantages to the zoom lens, and it’s a very versatile bit of equipment, but it does have significant drawbacks which could have an effect on how you use it in the future. You’ll be a better photographer if you have an understanding of the disadvantages of the zoom lens.