Following Jakob Nielsen’s advice to always maintain visibility of system status, I do think it is important that the user is aware of what is going on. So if you do implement infinite scrolling, it is important to have some form of indicator.
My personal choice for this type of design is a hybrid, similar to the Facebook and Twitter apps, as well as Google Images on web, whereby there is a “Load More” button if you scroll down, but then if you keep scrolling it has the same effect as clicking the button. The button enables infinite scroll, either for a fixed amount of posts, or completely. This affords mouse users the opportunity to determine when to proceed, and mobile users have the same option but a very natural experience (as you say, scrolling is commonplace on mobile now).
Example. Image credit: plasticmind.com