Is there any evidence that they didn't do the required checks ?
It's a good point jassi, and I must admit I don't have any evidence beyond the article quoted earlier on this thread by a former employee. That is evidence of sorts.
I think it's clear however that Mark Warner and probably other companies of the type take advantage of the cheap seasonal work available, and do not employ their young student-type workers on the basis that one would hope an older or permanent worker would be employed, with regard to pay, training, care to observe the various legal requirements, and so on.
We also know for a fact - on a slightly different but related issue - that MW had no security arrangements in place at the Ocean Club. (This was discussed at length on earlier threads ).This was also obviously a cost-cutting issue, which may have been a factor in Madeleine's disappearance and also in the burglaries that ocurred around that time. MW also apparently failed to alert guests to the fact that there was a level of possible crime in the resort, and again this may have been a factor in certain things.
I don't want to get into a discussion about parental responsibility again; obviously parents and guests have their own responsibilities with regard to their safety and property over and above the arrangements of the resort. But MW's evident laxity in these areas, in the circumstances, cannot be ignored.