Buying a business can be more complicated and have greater tax ramifications then one may first realize. Generally speaking there are two different values to a company, the book value and the actual value. When you are buying a company with significant assets there will be significant research, perhaps by a business valuation company, into the value of the company and all of these ramifications will hopefully be taken into account.
Where the interesting situations arise is when there is purchase of a company that has limited assets or is not valued very high. Both the purchaser and the seller have to realize that there can be tax ramifications based on the value of items that you may not conventionally think of as assets. These assets include client lists, name recognition, and repeat customers; all of these things have value and Uncle Sam is not going to simply let it slide that you did not account for them as part of the purchase. It is a nice reminder that for all business purchases, large and small, that an accountant and attorney should be consulted to help ensure that there are not any unforeseen consequences of your business purchase.