I think I may have got 3 wrong...

Most cable and DSL connections are on a contention ratio - anything from 10:1 up to 50:1. This means that the bandwidth is shared with other users on the same line (or perhaps the same exchange).

If those other users have the gall to use the connection at the same time as you then your download speeds will be slashed. But chances are they are downloading rather than uploading so your upload bandwidth will probably still be quite good.

I don't think there's much you can do about this short of buying a dedicated line.

Mark

P.S. Could the people sharing my line please stop downloading. Thankyou. :^)