The Ministry of Magic seems a really friendly place to work. It's like everyone there knows you on a first-name basis. Consider Arthur Weasley's encyclopedic knowledge of his fellow Ministry employees at the Quidditch World Cup.
Their tent seemed to be pitched right alongside a kind of thoroughfare to the field, and Ministry members kept hurrying up and down it, greeting Mr. Weasley cordially as they passed. Mr. Weasley kept up a running commentary, mainly for Harry’s and Hermione’s benefit; his own children knew too much about the Ministry to be greatly interested.
“That was Cuthbert Mockridge, Head of the Goblin Liaison Office...Here comes Gilbert Wimple; he’s with the Committee on Experimental Charms; he’s had those horns for a while now...Hello, Arnie...Arnold Peasegood, he’s an Obliviator - member of the Accidental Magic Reversal Squad, you know...and that’s Bode and Croaker...they’re Unspeakables...”
(Goblet of Fire, Chapter 7, Bagman and Crouch).
Mr Weasley knows everyone. And everyone knows him. Even the random witch who checks people's tickets on the way into the World Cup stadium knows him personally.
“Prime seats!” said the Ministry witch at the entrance when she checked their tickets. “Top Box! Straight upstairs, Arthur, and as high as you can go.”
(Goblet of Fire, Chapter 8, The Quidditch World Cup).
Is this just a case of Mr Weasley being a generally stand-up guy that everyone wants to know? Or is this a case of the Ministry of Magic being an organisation where everyone is on first-name terms? I understand that the wizarding community is a relatively small, tight-knit one, and some people will obviously know one another from their school days. Yet the Ministry must employ hundreds if not thousands of people. I mean, in Deathly Hallows they have a dozen people working solely on pamphlet production. That's a lot of names to learn.
Do we ever see anyone from the Ministry not knowing a colleague's name, or failing to address them by name? Is it reasonable to suppose that everyone who works at the Ministry literally knows every single other employee by name?