Via Venture Blog :
What are the costs involved in the Long tail businesses:

1. Search Costs :It is not enough for a company to aggregate lots of small things. Reducing search costs by matching content to users is critical for Long Tail businesses.
2. Psychic Costs:These measure the stress of having to think about a transaction.The psychic cost of stressing over your minutes outweighs the extra money paid for an unlimited package, so long as the total costs are fairly low. This is one of the reasons microtransactions for content have not really taken off.