There's always a possibility when a company is bought or merges or goes bankrupt and someone else picks up the pieces that there will be a short-term disruption as systems are intertwined.

NPR: Wall Street Woes: Who Gets A Bailout?

If she and her husband are travelling or are stuck at their desks, there is someone else to feed their kids and read to them.

NEWYORKER: A Woman��s Place

If he leaves his property unattended, there is a danger that the chief will give his land to someone else, or that a sibling will grab it.

ECONOMIST: No title

The same sort of thing exists on the internet where there is nothing technically that stops someone from doing Denial of Service attacks or from breaking into a system, or anything else for that matter.

BBC