These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Crazy Stupid Love
Fridge Logic: Liz is presumably a very close friend of Hannah's. Has she never met Cal or seen pictures of him, enough to recognize that he's the guy Jacob is with at the bar? Not only that, but it appears that Hannah goes to the bar fairly often, yet never once ran into her father there.
Also, do none of these women that Jacob sleeps with then never calls again ever return to the bar?
Hannah pretty much puts her social life on hold in order to study for the bar exam. She stops going out the same time Cal starts frequenting the bar. And Liz might only go to that bar with Hannah, rather than by herself.
Harsher in Hindsight: Robbie cites Ashton Kutcher and Demi Moore as an example of a younger man/older woman relationship that's gone strong. Cut to a year after the film's release...
Hate Dumb: In-universe. Hannah's friend's reason for disliking her fiance is solely that he's nerdy and boring. Jacob is hot and fashionable so the fact that he's a womanizer is a non-issue with her.