I love the concept of tapas. Since dinner is served so late in Spain, tapas, a variety of small appetizers, serve to keep Spaniards from suffering from hunger bouts between work and dinner. What I love about tapas is that it allows people to eat a diversity of foods in one meal. One can reasonably eat four tapas for the price of one entrée.
In Spain, tapas precede dinner. But, I see no reason why tapas-style appetizers should not constitute dinner. Most entrees have diminishing returns. As you eat more of an entrée, that entrée becomes less pleasurable. Some of this can be attributed to decreased hunger but much of it can also be attributed to decreased novelty. The first taste of a delicious flavor does more for you than the 35th taste of that flavor (there, arguably, are exceptions: lobster may be one). The last bite of that steak or chicken is rarely as pleasurable as that first bite. Rich foods like creamy pastas tend to have significant diminishing returns. Anyone who has ever eaten penne alla vodka can attest to this. Moreover, one of the benefits of going out to eat at a restaurant is that the chefs cook for far more people (who have varying tastes) than you probably do at your home: as a result, its easier to order a variety of dishes than it is to cook a variety of dishes.