When you really need to prepare for a great event, where you know that there are going to be over 1000 participants then you really have to take the organising procedure of that certain event as a priority - you have to hire a couple of experienced people that will organise everything, you need to create all the promotional materials, you need to evaluate all the things that can go wrong and calculate afterwards what can go wrong and in what way.
And when everything will seem to be fine, when all the things are going to be planned, all the contractors are going to be either hired or paied, then you can be sure that some new things are going to arise from God knows where, and some issues are going to generate a couple of problems. This is why you need a lot of experience in organising things.
And in our case, the biggest problem was with the rental car companies, that were unable to provide us witha nive black cab in Bucharest - as they are only doing car rentals for mainstream purposes or low end cars that were not fit to our actual tasks. So we discovered that we needed those black cabs and searched a lot in Bucharest for that kind of cars - which finally led us to Rent car with Driver - a company that is very serious from a business point of view, a company that has the best black cabs in Bucuresti and also very good pricing and conditions.
So - after finishing the job with the car rental company we were ok - no more surprises arised regarding our event, which in fact worked 100% as planned, and everyone was more than happy with the experience - especially the guests, that really had a good time in Bucharest.