Question: Why is it said that BitTorrent is faster, partly, because it transfers random pieces of a file instead of transferring it from start to finish in a contiguous/linear fashion?

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**EDIT:** But why do they *have* to be 'random'? Why not a more predictable 'semi-contiguous' transfer in which one peer gives you the first half, and the second peer the other half? This would theoretically reduce overhead.

Answer: 
It should be said that this depends entirely on the file in question, amount of peers and speed of the non bittorent source.

You will never download faster than the maximum download bandwidth of your connection, and if you are downloading from a place with enough bandwidth, it will be faster than using Bittorrent.

However, as internet speeds are getting faster and faster, we are getting to the point where (smaller) websites and hosts can not keep up.

For example, when I was looking around at colocation prices up in London a few months ago, I was quoted absolutely terrible prices for a 5Mb connection. If I was to take this, it would serve the majority of people well.

However, on the same line, if I was to host a few 500Mb files, and everyone had Cable (50Mb) or fast ADSL2+ (24Mb) lines, you would notice that my server would not be able to serve up speed that fast to you...

... however, if I was to offer you the same file through Bittorrent and there were 200 people, each giving just 30Kb/s, that would equal 5.8Mb/s (and, many people have much faster upload speed than that!).... and now, if I was to run Bittorrent on my server and offer the same file, it would mean that there is a total of 10.8Mb/s downloadable - much more than I could provide through that 5Mb/s pipe on my own.

Bittorrent is very much a numbers game, you have to have enough people uploading with enough bandwidth... Because of extra steps involved such as integrity checking (and the fact that you **should** upload back), it is hard for it to ever beat direct downloading from a good site with enough bandwidth, but, for many smaller sites - it is brilliant or even larger sites who simply want to save money off their bandwidth bill.
Most responses don't seem to be answering your question.

**BitTorrent is not faster.**

It's actually *slower* because of the overhead of connecting to multiple sources.

The real difference in practice however, is you are downloading from many sources that can **potentially add up** to be faster than what a website could give you. Many web servers are under heavy loads or are otherwise speed-limited so you don't suck them dry.

The fact that BitTorrent transfers the file in a seemingly random order has no direct affect on its speed.

In regards to your edit, the **pieces are not random!** They are prioritized based on rarity: a rare piece needs to become less rare as fast as possible so it is not lost if the source that has it suddenly leaves. It has to do with availability, not speed.