How Excessive Government Killed Ancient Rome by Bruce Bartlett is definitely worth the read. Bartlett gives a compelling argument regarding the fall of the Roman empire. The article points to the growth of imperial power in Rome (bureaucracy) as the seeds that ultimately destroy the civilization. For example, many of the early emperors devalued the coinage within the empire, this resulted in inflation as well as higher taxes.
The general accepted history is that the Roman empire 'fell' in 476 A.D. in the west because it was just too big, too far off to manage properly, however the empire lived on in the east until 1453 A.D. when the Ottoman Turks sacked Constantinople. Obviously there is no shortages of opinions with regard to your question but I think Bartlett's article gives tremendous food for thought.
There are so many of these.
The most famous argument was by Edward Gibbon, which said that Rome fell largely because of the spread of Christianity. He says that the religion caused Rome to be less warlike and that allowed the barbarian invasions to succeed.