For the friends and family: We are quite safe. Yesterday morning, a cliff fell onto a bunch of multi-story homes in Cairo. The English-language news has described the area as variations of "shanty towns," "squatter towns," and "informal communities." Basically, Cairo is dense and there is a vast differences between the rich and the poor, and of the latter, there are around 2 million people who live in homes which have been built on its outskirts. They don't officially own the land (it is not officially Cairo), there is no running water or utilities, no formal governing structure. This happened on a weekend morning during Ramadan, when entire families would have been home together, enjoying the holiday. Most of the people living in these communities have come to Cairo from other parts of Egypt, seeking work and a better living for their families. Many are immigrants and refugees. They are forced into such parts of town due to a lack of options and the high cost of those options which do exist. They are overtly disregarded by the government and upper classes, and are often directly blamed for their hardships. When the same thing happened (killing 30) in 1993, the people who died were blamed for living there. The same seems to be true now (from CNN):

"We are following the case step by step and providing the care and comfort for the residents," Prime Minister Ahmed Nazif said in a statement. "We would like to remind people the danger of building informal housing in dangerous areas."

Here is an article from CNN, which does a good job highlighting the indifference of the people in charge: Hundreds feared trapped in Egypt rockslide