Have a look at the PDF he links to at the bottom. They sent the standard cease and desist takedown notice. His post shows just how beneficial a real lawyer is in making legal decisions (note, he's not being sued and the letter doesn't say "we'll sue you").
"hand over your business, your domain and your software within 12 days" or we'll see you in court
and
"Being Sued" ?
I know the letter is a cease and desist letter but the we'll take leagal action hardly makes it a 'thanks for adding value to the twitter ecosystem love letter'