On a typical LEGO box, three edges of the box are continuous and one is glued. It used to be that the ends, which now have tape seals, were also glued shut. I have a feeling that AFOL’s complained that the boxes got damaged when they were cut open, so the current style of seals were added. How sneaky it is then not to touch the seals and to open the one edge that can be sliced and reglued.
One problem with checking my unopened sets is that the sets cannot be returned after 90 days for most retailers, so I am stuck with everything older than 90 days. Also, my storage system is not exactly archive quality … a better word to describe it would be haphazard. Regardless, I know to check for more signs of tampering both in sets I already have and ones that I want to buy. I would suspect that online retailers like S@H and Amazon are less likely to have this problem.
That is diabolical, especially since most minifigs are in separate baggies. The thief must have purchased the set, taken out the minifigs, resealed the box, and returned it as “unopened” to the store. If they paid cash, it would be nearly impossible to track them down. I rarely buy sets from retail stores anymore (mainly from S@H or a Lego Store) but would be really p-o’d if that happened to me. Greg, are you going to open any of your sets to see if they are intact? You could still list them later as MIB with a notation that the box was opened only to verify that the minifigs were intact.