Facebook

Facebook's Feed is the canonical infinite feed, and it carries the weight of trying to be everything. One vertical column interleaves a friend's post, a Group you joined years ago, a Marketplace listing, a Reel, and several ads styled to look like organic posts. The ranking is opaque; the same status update may surface days late or never. Density is the defining problem. Nested comment threads, a reaction tray on long-press, share sheets, and event invites all compete inside each card, and the chrome around them has accreted over the years. Navigation lives in a tab bar that reshuffles by region and test cohort, so muscle memory rarely holds. The long-press reaction tray, a row of emoji beyond the plain Like, is one interaction that aged well.