It's both really.  At least for us at Cutcaster.  You need to figure out a lot of the metrics to determine what the costs are surrounding the acquisition of a new buyer and once you figure that out you can determine if it makes sense and you want to spend your money to scale that part of your business to get more buyers.  it could include pay per click advertising, print advertising, direct sales calls or finding distribution through biz dev partnerships. All cost different amounts but determining the return on each investment is what i think will seperate the winners from the losers.  That is a bit of stream of conciousness so hope it helps.  I can write in more detail later if you want.