Part of the problem with those is that a lot of companies (including big ones) have started sending notification and "what's happening" updates them without an

Part of the problem with those is that a lot of companies (including big ones) have started sending notification and "what's happening" updates them without an opt-in, which causes users to think they're spammy and mark them as such. LinkedIn and Twitter are particularly big offenders here, but there are a lot of others. Twitter even likes to periodically invent new kinds of email notifications and newsletters, and opt you in to them by default. Gmail might be making this a little better by introducing a middle ground, moving those kinds of emails out of the Inbox into either the "Social" or "Promotions" boxes, where they're less likely to be marked as spam (although probably also less likely to be seen).