Please, talk to each other. It's important to linguists that there should be plenty of chat. We need language live, on the hoof. Millions of spoken word tokens everywhere, so that we can (for example) compare Donald Trump's amazingly high proportion of first-person singular pronouns to the average for non-narcissists like typical Language Log readers.
However, beware of engaging in chat to strangers on the subway if you are in London. A new campaign for people to wear a "Tube chat?" button when traveling on London Underground trains, intended to provoke random conversation with other passengers, has been met with horror and disdain by the misanthropic curmudgeons who use the services in question. No chat please; we're Londoners.
[Comments are turned off out of respect for readers in London.]