Borders come in for a lot of stick these days, but they do some good. I like being able to go across from the UK to France to buy stuff, including drink, at lower prices and rates of duty. I really like being able to cross the Oresund Bridge between Denmark & Sweden and buying in each country what costs more in the other.

In the US I like to cross state lines to go for the lower sales taxes and duties. It is reckoned that 'leakage' (cross border shopping) will be a significant factor if there is a 3 percentage point tax differential. And it's not only competition in sales and purchase taxes which works. I love French food and wine, and the priority they are given, but I don't feel the same way about their income tax and social insurance. The Danes do pickled fish on rye bread superbly, but there's no way I want to pay Danish taxes. I enjoy the Swedish forests and lakes, but not their government.

Borders let me enjoy the best of each country, while being able to avoid the worst. Beware of Eurocrats speaking with forked tongue about tax harmonization. It's tax competition we want.