Apathy Sketchpad has an excellent article musing on the problems of delivering a truly random sequence. Not only is this very hard, humans are also exceptionally bad at recognising a truly random sequence when they see one:
Unfortunately, it's very difficult to tell if your numbers are random enough or not. For example, some episodes of the dreary logical fallacy roadshow that is Deal Or No Deal used an Excel spreadsheet to randomise the assignment of 22 sums of money to 22 boxes -- for which there are probably more sequences than there are grains of sand in the world -- and the seeding was bad enough that only twelve of them arose in over forty shows. You can experience this for yourself: whether by accident or design, the Concentration mini-game in Super Mario Brothers III only ever shows players eight out of a possible 58 billion permutations of cards. The producers of Deal or No Deal switched over to drawing lots by hand.