thousands of congratulation vs thousands of congratulations

Some examples from the web:

• A thousand thanks, and congratulations on the result of the referendum.
• A final word of congratulation to the Luxembourgers.
• Commissioner, it is time someone in this debate sounded a note of congratulations.
• So... Please hand this letter of congratulations to Dwight K. Schrute.
• Speaking of congratulations l guess l should be passing some on to you.
• Commissioner Piebalgs deserves a great deal of congratulation for declaring energy efficiency to be his priority.
• In September, several governments and the President of the Commission sent him messages of congratulation.
• In fact, I was expecting a word of congratulations from you...
• Mr. Lassiter taught thousands of students.
• Thousands of people are there paying their respects.
• Apparently there are thousands of people waving, cheering...
• One mistake in thousands of operations.
• Ourforebearers settled the Vale thousands of years ago.
• Treason that risks hundreds of thousands of lives.
• Thousands of people's medical records.
• These things take thousands of years.
• We see people travel thousands of miles across state lines.
• Aaron was hit with thousands of malpractice lawsuits.
• Birds eat thousands of snails every day.
• Thousands of protesters are demonstrating across Poland today...

Some examples from the web:

• A thousand thanks, and congratulations on the result of the referendum.
• A final word of congratulation to the Luxembourgers.
• Commissioner, it is time someone in this debate sounded a note of congratulations.
• So... Please hand this letter of congratulations to Dwight K. Schrute.
• Speaking of congratulations l guess l should be passing some on to you.
• Commissioner Piebalgs deserves a great deal of congratulation for declaring energy efficiency to be his priority.
• In September, several governments and the President of the Commission sent him messages of congratulation.
• In fact, I was expecting a word of congratulations from you...
• Mr. Lassiter taught thousands of students.
• Thousands of people are there paying their respects.
• Apparently there are thousands of people waving, cheering...
• One mistake in thousands of operations.
• Ourforebearers settled the Vale thousands of years ago.
• Treason that risks hundreds of thousands of lives.
• Thousands of people's medical records.
• These things take thousands of years.
• We see people travel thousands of miles across state lines.
• Aaron was hit with thousands of malpractice lawsuits.
• Birds eat thousands of snails every day.
• Thousands of protesters are demonstrating across Poland today...