(a) "The company we're buying is going to be worth a lot more in the future." (Presumably so is the interest in the old business that is being traded away; future prospects are implicit in the business valuation process. If 2X is issued for X, the imbalance still exists when both parts double in business value.)
(b) "We have to grow." (Who, it might be asked, is the "we"? For present shareholders, the reality is that all existing businesses shrink when shares are issued. Were Berkshire to issue shares tomorrow for an acquisition, Berkshire would own everything that it now owns plus the new business, but your interest in such hard-to-match businesses as See's Candy Shops, National Indemnity, etc. would automatically be reduced. If (1) your family owns a 120-acre farm and (2) you invite a neighbor with 60 acres of comparable land to merge his farm into an equal partnership - with you to be managing partner, then (3) your managerial domain will have grown to 180 acres but you will have permanently shrunk by 25% your family's ownership interest in both acreage and crops. Managers who want to expand their domain at the expense of owners might better consider a career in government.)
(c) "Our stock is undervalued and we've minimized its use in this deal - but we need to give the selling shareholders 51% in stock and 49% in cash so that certain of those shareholders can get the tax-free exchange they want." (This argument acknowledges that it is beneficial to the acquirer to hold down the issuance of shares, and we like that. But if it hurts the old owners to utilize shares on a 100% basis, it very likely hurts on a 51% basis. After all, a man is not charmed if a spaniel defaces his lawn, just because it's a spaniel and not a St. Bernard. And the wishes of sellers can't be the determinant of the best interests of the buyer - what would happen if, heaven forbid, the seller insisted that as a condition of merger the CEO of the acquirer be replaced?)
Later in the letter Buffett goes on to say...
Managers and directors might sharpen their thinking by asking themselves if they would sell 100% of their business on the same basis they are being asked to sell part of it. And if it isn’t smart to sell all on such a basis, they should ask themselves why it is smart to sell a portion. A cumulation of small managerial stupidities will produce a major stupidity - not a major triumph. (Las Vegas has been built upon the wealth transfers that occur when people engage in seemingly-small disadvantageous capital transactions.)
A good relatively recent example of this is Kraft's purchase of Cadbury.