Topping is the worst thing you can do to a tree. When I was in Hawaii working for companies that topped trees I remember customers asking me if it was necessary to be so drastic with the trees. Since I no longer work for those companies I can be less evasive and say, no. I never felt comfortable topping all of those beautiful trees. It was sad to do so much irreparable damage. There is hardly ever a time when a tree should be topped. One of the rare exceptions is when a tree has died back on it's own such as the recent frost that damaged so many ficus trees.
Many people are afraid of their trees because they have grown so large. It can be intimidating living in the shadow of a giant. Ironically the most dangerous tree is one that has been topped. When a tree is topped the suckers that grow from the ends of the cuts grow very fast. In general a tree will have recovered its former height within 3-5 years of being topped. Normally fast growth equals weak growth and the opposite is true as well. The suckers that are frantically growing to produce leaves will be very weak. Another factor which contributes to the sucker's tendency to shed is the fact that the new growth can only be attached at the outer most part of the branch. In other words a normal branch has a kind of root inside the trunk. The bigger the trunk and branch get the better the attachment. A sucker starting on the outside of the trunk will be poorly attached and have a tendency to fail. Many people over-estimate their trees capacity for damage in a storm. I have seen 80 foot tall Eucalyptus trees fall directly on a house and do no structural damage. Of course I have seen properly thinned trees not fall over at all! In my opinion the height of a tree has little to do with the tendency to blow over in a micro burst. Thick, overgrown trees are usually the ones to fall.
What if your tree has already been topped?
In the tree service industry a knowledgeable arborist should understand the concept of "Crown Restoration." After a topping cut is made an experienced arborist can attempt to repair the damage. Usually about 5-8 suckers will fight for dominance on the end of the topping cut. In some trees they seem to repair themselves by causing the weakest suckers to fall off. That isn't the best or safest way to do it. The only way to repair a topped tree takes anywhere from 3-5 years to accomplish. It involves selective thinning of the sucker growth. For example: year one remove two suckers, year two remove two more suckers and so on. The finished product will have a thicker trunk with one large sucker growing from it. Over time the sucker will develop a stronger attachment to the trunk. It just depends on the circumstances as to how many prunings will be needed to get to this point. Right about the time when you are feeling like the crown restoration is complete it may be necessary to reduce the height of the tree through proper reduction cuts.
In brief, never let anyone top your tree. As a consumer it is important to know what a good cut looks like so an informed decision can be made about who will work on the tree. Many companies actually advertise "Topping," raise an eyebrow when you see this.