If you're up for a long read, here's a link to a posting to the Hobbes list from Bill McCready back in 1996 that gives Santana's perspective on rear hub spacing and the evolution of the 145mm and 160mm standards: http://search.bikelist.org/getmsg.as....9604.0451.eml
This link 'should' take you to one of the various volley's back-and-forth on the subject of 145mm vs. 160mm which, to this day, remains a polarizing subject:
The only conclusion that I've come to is that tandems can be built with everything from 130mm to 160mm to accommodate different requirements and wheel reliability comes down to the same thing: the wheels need to be built to support different requirements and wheels that use better-matched components (hubs, spokes & rim) and that are built with more attention to detail (proper spoke count for team weight, proper spoke tension and thorough distressing) will out last wheels that aren't.
So, while in theory a 160mm wheel with hub flanges that are spaced further apart than a 145mm hub's flanges hould have more lateral strength, if the spoke tension is a bit off on the 160mm wheel that theoretical additional strength will become a moot point when a spoke breaks and reliability comes into question.
As for current flange spacing, the 160mm hubs do tend to have wider-spacing vs. the 145mm hubs and many of the 145mm hubs used the same hub bodies as 135mm mtb hubs. All of these hubs can be used to build wheels that will offer very good lateral strength and durability and, as you'd expect, be found on wheels that weren't built well, were damaged or lost uniform spoke tension over time that have a history of breaking spokes.
tandem_rider is also correct in that the wider rear axles used on tandem hubs also allowed for easier installation of the Arai drum brakes.