Known Relative Studies with 23andMe: Expected Percentages

I have had quite a few known relatives test with 23andMe recently. In the coming months, I will be writing a number of posts based on these results. As an introduction, I wanted to review some of the information that 23andMe and FTDNA provide in their FAQs regarding their autosomal DNA tests, Relative Finder and Family Finder.  All of these percentages are estimates and will vary due to the random nature of genetic inheritance. The following statistics apply to both 23andMe's Relative Finder (RF) and FTDNA's Family Finder (FF).

Expected percentage of shared DNA between:
Parent/child/siblings = 50%
Grandparent/grandchild/aunt/uncle/nephew/niece/half-siblings = 25%
1st Cousins/great-grandparent/great aunt or uncle/grandnephew or niece = 12.5%
1st Cousins once removed = 6.25%
2nd Cousins = 3.125%
2nd Cousins once removed = 1.563%
3rd Cousins = .781%
4th Cousins = .195%
5th Cousins = .049%
6th Cousins = .012%
7th Cousins = .003%
8th Cousins = .001%

The likelihood of detecting shared DNA with a known relative significant enough to show up in RF or FF:
1st Cousins and closer: 100%
2nd Cousins:  > 99%
3rd Cousins:  ~ 90%
4th Cousins: ~ 45% (FTDNA says > 50%)
5th Cousins: ~ 15% (FTDNA says > 10%)
6th Cousins and more distant: < 5% (FTDNA says < 2%)

In some families, there will be situations that will complicate the above predictions, such as cousin marriages and half-siblingship, but, in general, they are the guidelines that should be used in analysis and comparisons.

Further reading from this series -
Known Relative Studies: Great Grandchild Inheritance
A Success Story and the Randomness of Autosomal DNA Inheritance (Fourth and Fifth Cousins)
Known Relative Studies: Second Cousins 
Known Relative Studies: More Second Cousin Comparisons 
Known Relative Studies: Second Cousin Comparisons, Allen Great Grandparents
Known Relative Studies: Second Cousins or Half Second Cousins 
Known Relative Studies: Identifying DNA from Great Grandparents Using Second Cousin Comparisons
Known Relative Studies: I Found My Third Cousin Today! 
Known Relative Studies: A Third Cousin Comparison and More Random Autosomal DNA Inheritance
Known Relative Studies: Purdy Fourth and Fifth Cousins
Autosomal DNA Matching and the Importance of Testing Multiple Family Members (Ninth Cousins)
Ratekin Seventh Cousin
A Second Cousin Adds to My Chromosome Map and Answers a Nagging Genealogical Question