Buying drinks can also be seen as someone weaker (financially) asking someone stronger. Considering that men earn more on average than women, and if you are picking up college girls and have a real job that is likely to be even more the case. So I don't see the way that these situations can be easily distinguished that way by someone without much social experience
I have a few meta-rules of thumb in such matters:
Anything can mean anything.
Corollary: Never explain by malice that which is adequately explained by intelligence.
The rules are never what anyone says they are.
The rules may not even be what anyone thinks they are.
Nevertheless, there are rules.
It is your job to learn them, and nobody's job to teach them to you.
All advice, however universally it may be expressed, is correct only in some specific context.
Application of the last to the whole is left as an exercise. :-)
This whole list is brilliant. Particularly,
Corollary: Never explain by malice that which is adequately explained by intelligence.
This makes "Never explain ... stupidity" a special case of this rule!
Followup to: Do you have High-Functioning Asperger's Syndrome?
LW reader Madbadger uses the metaphor of a GPU and a CPU in a desktop system to think about people with Asperger's Syndrome: general intelligence is like a CPU, being universal but only mediocre at any particular task, whereas the "social coprocessor" brainware in a Neurotypical brain is like a GPU: highly specialized but great at what it does. Neurotypical people are like computers with measly Pentium IV processors, but expensive Radeon HD 4890 GPUs. A High-functioning AS person is an Intel Core i7 Extreme Edition - with on-board graphics!
This analogy also covers the spectrum view of social/empathic abilities, you can think about having a weaker social coprocessor than average if you have some of the tendencies of AS but not others. You can even think of your score on the AQ Test as being like the Tom's Hardware Rating of your Coprocessor. (Lower numbers are better!).
If you lack that powerful social coprocessor, what can you do? Well, you'll have to run your social interactions "in software", i.e. explicitly reason through the complex human social game that most people play without ever really understanding. There are several tricks that a High-functioning AS person can use in this situation: