The only thing I can say about that for names in the Netherlands, is that the name shouldn't be 'ridiculous'. The person from the government who registers the birth of a child, can refuse a name if it is a 'ridiculous' name. This also means that he/she could refuse a name because there are a ridiculous amount of middle names. This only means that parents can't go giving their kid a limitless amount of MNs, but there is no fixed number.
btw: The most MNs I've seen on a person (except royalty) is 4.