Product placements vary in how they're done. When someone in a movie picks up a can of Coke, that's one thing, when everyone at the table picks it making sure that their fingers don't actually wrap around the can so that the primary logo, facing right at the screen, is clearly legible, EVERY TIME, it's intrusive.
In a book, I find it equally frustrating when authors go out of their way to avoid mention of something that would otherwise add detail and realism to the writing. Constantly referring to "cola" is one thing, but saying, "...ordered a Coke" might add insight to the character (remember the Laverne Pepsi/Coke stuff
)...but also sounds more natural. If the author goes crazy with it though, "...ordered a cool, relaxing, and refreshing Coke, and felt the urge to teach the world to sing..." it's going a bit far.
(Perhaps this pop/cola/Coke thing is an regional issue though...
http://popvssoda.com:2998/ )