Let's talk X (and similar constructions)
where X is a noun phrase, has a variety of possible interpretations / possible substitutions for 'talk', depending on the nature of X. These structures certainly look like transitive usages of 'talk', though how useful the 'verb + DO' analysis really is (they talked tripe / *tripe was talked by them / *did they talk it) for individual senses is arguable. From AHDEL:
- To utter or pronounce (words): Their son is talking sentences now. [Don't talk tripe.]
2a. To speak about or discuss (something) or give expression to
(something): talk business; talk treason.
b. Used to emphasize the extent or seriousness of something being
mentioned: The police found money in the car. We're talking
significant amounts of money.
To speak or know how to speak (a language or a language variety): The passenger talked French with the flight crew. Can you talk the local dialect?
To cause (someone) to be in a certain state or to do something by talking: They talked me into coming. [He's talking her to death.]
Sense 2a seems an obvious deletion of the preposition 'about' so that 'talk' is used at least superficially like 'discuss'. Prepositional deletion is not uncommon (I'll see you [on] Tuesday; they entered [into] an agreement; ...). It is often used to create a punchier variant. But being in the modern idiom, it may not sound natural when used with some older / traditional referents.
These Google Ngrams for "let's talk money", "they're talking politics" and "we're talking business" show that sense 2a above has been in use for quite a long time. General trends are hard to spot.
My impression that examples of sense 2a are widespread and common is supported by largish numbers of Google hits for "talking politics"; "talk money" ....
There are constraints on the actual noun phrase chosen. These seem to be for more subtle reasons than the avoidance of ambiguity.
Let's talk hip-hop.
?Let's talk plainchant. (incongruous)
?/??Let's talk weather. (unnatural sounding)
*Let's talk Mr Lee / the Simpsons / me.