I went to the 'Meet Meltwater' session along with 10 other candidates in Paris, France. The manager gathered us and delivered a little speech about the company. Then, we split into three groups and we attended three workshops in turns. The first was conducted by two girls - one from France and one from South Africa - and we talk about company's culture and ways of working. At the second workshop, we talked about sales. At the last one, a presentation of the product Meltwater sells.
I think the company is looking for candidates able to mingle in ways that are friendly, yet this 'let's mingle together' is already a competition. You must appear as natural as you can be and prove that you can ask relevant questions and - I think - make them laugh or smile. They are also looking for a teammate.