First of all, let me say that uploading a file that is not yet complete, or maybe even in the process of downloading is GREAT, since it helps spread the data around faster.

But I have a small concern about segmented downloading. I mean, getting the same file from multiple hosts at the same time. We all know that this will tie up many upload slots, which would prevent other users from getting files. The idea is that since you are getting less of the file, the slots will be released faster. That is all fine and good in an ideal world, but I think it won't work like that in the real world without some safeguards.

Let me just make an example. Let's say that there are 2 hosts with this very rare file. They have infinite upload bandwidth. Download bandwidth is limited in such a way that it will take an hour to download this file.

In the current situation, we have a timeline that looks like this:

0.00hours - 2 files on the network
1.00h - 4 files on the network
2.00h - 8 files on the network

Now, with an ideal situation in which we use segmented downloading and people have infinite download bandwidth, and each person uses every host available with the file:

0.00h - 2
0.50h - 3
0.83h - 4
1.08h - 5
1.28h - 6
1.45h - 7
1.59h - 8

So we got to the same number of copies in less time, which is always good. But now, lets thing about someone with very limited download bandwidth trying to do the same. Lets say that even if they get a whole lof of segments going, they will never be able to get it faster than in one hour:

0.00h - 2
1.00h - 3
2.00h - 4
3.00h - 5

In this case, the file spreads much slower.

Of course, since we are always uploading little chunks, the "graphs" will look different, but we can't ignore the fact that slow bandwidth people will destroy any benefits that segmented downloading might offer. Segmented Downloading can work, but we need to study the bandwidth that each servent has available to it, and adjust the limits according to that. Sadly, the user cannot be trusted to tell us how big is their pipe.

Please let me know if I am completly wrong on this!