Teeter-Totters, Musical Chairs and Tug of Wars: The World of Multistate Income Taxes

Over the past week I have been preparing to deliver a state income tax presentation in Richmond, Virginia and Norfolk, Virginia on May 23th and May 24th.  My agenda includes:

1. Major legislative developments
2. Nexus
3. Combined reporting
4. Discretionary authority
5. Tax base
6. Allocation and apportionment
7. Miscellaneous developments

As I have prepared the material, a few main thoughts stick in my mind:

1. State income taxes remain to be deceptively simple and endlessly complicated
2. The 6 most used words in the state income tax consulting world are:  "generally" and "it depends on the state"
3. In the world of state income tax, there are many battles in the never ending war; meaning, you win some, you lose some (i.e., tug of war, musical chairs)
4. The states are focused on increasing taxes on "out-of-state" taxpayers
5. Economic presence is enough to create nexus in some states
6. Combined reporting continues to be popular
7. Market-based sourcing of sales other than sales of tangible property continues to spread like wildfire
8. The burden of proof regarding changing apportionment methods, forcing combined returns, and ultimately, tax assessments switches between the taxpayer and the state like a "teeter-totter"
9. The add-back of intangible expenses paid to related parties is still scrutinized, but exceptions may apply
10. Single-sales factor apportionment will soon be the only apportionment method??
11. State amnesty programs still exist, but may not be better than a good old Voluntary Disclosure Program

What do you think of when you think of multistate income taxes? 
(I know, I am assuming that you think about multistate income taxes)