"FTP server" set off a red flag for me, as I know it's something that not all cable ISPs allow (servers on their connections).
Found some funny info on Optimum Online. Apparently, they practice a very interesting practice of capping the upload rates of their subscribers by at least 1/3 if they upload at the full connection speed for more than a few minutes. The only evidence they have that this is fully acceptable and that the user is actually getting what they're paying for is a clause in their agreement that says that they'll take whatever means necessary to maintain the security and stability of their servers. Optimum Online does not alert the user that this has happened, and will only inform them once they call that on the fourth occurence of this, their service will be terminated.
The "Boost" version of the service apparently allows servers to be run. I'm guessing that the standard service agreement forbids running a server, since I've only seen the Boost service mentioned with servers (To the exclusion of normal service). The website has no effective way to compare the two, however. Furthermore, OO has apparently stated that capping also applies to servers running on the Boost connection.
So I'd say that by running any kind of server, you're putting your connection speed/existence at risk.
And if you need to ask people whether or not your uploads/downloads with a certain filesharing program can be monitored, I'd make a wild guess that you may be thinking about doing something not entirely legit.