It's OK to do that occasionally, but not all the time.
Most of the time it is safe but you should ask your doctor because it might not be safe for you based on your paticular pill and/or medical history.
If you are on a single-dose pill, skipping the sugar pills will work to make you skip your period. If you are on a three-dose pill (usually 3 different colours too) you can only delay it for one week by taking the third week of a second pack immediately after the third week of your first pack. It means you waste a pack.
Secondly, your period while on the birth control pill is NOT a natural menstrual cycle, so skipping it is not harmful. Just listen to what your body tells you. It works for some people, but not others.
I agree with the last answer 100%. It's totally safe, but it doesn't work for everyone. I had small spotting for the whole month after I tried skipping. My best friend can skip without problems though.
ANSWER
I've been on birth control now for 3 years. if you are taking a pack with 3 weeks of active pills and 1 week of placebo, or sugar, pills, then it is completely OK and 100% safe to skip the sugar pills and continue taking active pills. But i strongly recommend doing this only if you've been taking the pills for 4 or more straight months. Doing this immensely reduces the chance of having spotting.