I try not to let what is most convenient for me get in the way of the general good when I write about politics, particularly the politics of other countries. Hence I have had to double-check my logic before writing about calls for the ending of the US' visa waiver program for Europeans, because it would be exceedingly inconvenient for me to be required to obtain a visa before entering the US, despite the fact that I have in fact obtained visas to travel and work in the US in the past. However after that rethink I remain against the idea of ending that program, indeed I think it probably should be extended somewhat, for a couple of reasons. [Note that the second link (to an AEI/Weekly Standard article) has much to recommend it and I agree with almost all of it except for the bit about the Visa Waiver program.]
The first reason why I disagree with it is that it is unlikely to actually prevent anything. Although occasional terrorists/potential terrorists may be stopped (e.g. the 20th 9/11 hijacker) because of the actions of consular officials and border agents, the porousness of the US-Mexican border is such that any European muslim who felt like penetrating the US could simply fly on holiday to Mexico and then walk north and probably, with a certain amount of preparation, they could take a holiday in Canada and walk south. Even if the border patrols on both sides were given more funding etc. it is hard to imagine that they would be able to actually close the border tight short of putting in fences and armed guard towers every three miles to create a modern day Hadrian's wall. Given that the US Mexican border is about 2000 miles long and the Canadian border even longer (nearly 4000 miles excluding the extremely tough Canada/Alaska border) the price tag of such a border fence is practically unaffordable (not to mention the question of where you would find the border patrol agents to man it in an economy that is already at effectively full employment or how you would pay them given the US govenment's enormous budget deficits). Even if there were not the open continental borders there is the question of whether the visa application process would in fact weed out the terrorists. Given that, contrary to (European) public opinion/expectation, most terrorists are both relatively well educated and affluent, it is hard to see what would show up potential terrorists compared to their non-terrorist neighbours who are visiting as genuine tourists or businesspeople.
The second reason I disagree with scrapping the Visa Waiver program is the economic impact it would have. Of course the US should be sublimely uninterested in the effect it would have on Europe so I will ignore that, but I believe that its effect on the US would be non-trivial. In 2004 there were appoximately 10 million European tourists to the USA, approximately half of the total number exlcuding (Mexicans and Canadians) . Assuming that 50% of them spent $1000 on a ticket through a US airline and they spent an average of 1 week at motel 6 nights and macdonalds dining rates (say $50/day *7 = $350) then the total spend of European tourists with US entities is $5Billion (flights) plus $3.5Billion (accomodation) or $8.5 billion, a number which is almost certainly a significant underestimate of the actual total. Another way of looking at the data is to look at the expenditure total ($94 billion) and estimate how much of that is applicable to Europe - taking a SWAG (scientific wild assed guess) of 25% and rounding up a bit we get $25Billion. Given the existence of Eurodisney, cheap airlines etc. it seems not unreasonable to guess that something like 20% of the tourists wouldn't bother to come to the US if the visa process were expensive and/or complex (a non-complex visa process is effectively worthless so I'm going to assume that a complex one including a mandatory interview with a consular official would be implemented). This means that anywhere from $2 Billion to $5 Billion would be taken out of the economy directly at a minimum. The US annual GDP is around $10 Trillion so this is a pretty small sum in proportion but it would hit some parts of the US economy heavily and does exclude the indirect costs of such a program which would probably be far greater. It is unclear to me how many Europeans make business trips to the US, how much that would be affected by a visa requirement and whether Europeans would buy less of they found it harder to visit their US suppliers but even knocking a few percent off the €157 Billion that Europe imports from the US each year would be painful. In total the trade and tourism impact of a visa requirement could easily be $10 billion per annum (and I reckon that would be a low end estimate) and I could imagine this cost being exploited by all sorts of short sighted politicians eager to get (re)elected.
The problem in crude economic terms is how much would a terror attack cost the US and for that matter what is the life of a US citizen worth? Answers that come up to less that $10 billion (per year) mean that in strict cost/benefit terms implementing a visa requirement costs more than is gained by doing so. Given that I don't believe (see reason one) that such a requirement would actually stop determined terrorists anyway all that scrapping the program does is cause significant hit to the US economy for no gain what so ever. Mind you the DHS and TSA have implemented all sorts of "security" measures in the US post 9/11 which seem to have significantly raised the costs of travel for limited benefits so perhaps I shouldn't expect logic to be applied to this issue, but I can always hope.