Yes I was hoping for a reply on this too I have to do a 2 tiered wedding cake soon and wonder if I should use alot of support.
anthing taller than 4", I would dowel/support.
Most two tiered cakes can be supported by either dowel rods, you can get them at any craft store), or drinking straws is another common tool used. Just make sure you cut them to the height of your cake and no more or your cake will be lop-sided. And put a cake plate under the top tier so it can be supported by the dowel rods and you should have no problem.