I'm close enough to my RT to get 6/768 on ATT. Effective speeds are about 5.1/650. That's enough to get theoretically 637KB/sec. 600 is definitely possible. 600KB/sec * 10 sec = 6MB * 6 = 36MB/min * 60 = 2160MB/hr * 24 = 51,840MB/day * 30 days = 1,555,280MB/month - 1.5 TB per month! So yes, DSL could hit any of the "caps" I've heard of. And yet, ATT has never complained about anybody using too much bandwidth.
I seed at about 75-80KB/sec 24/7 and have had no complaints. I seed at about 50-58KB/sec on my RR and have had no complaints and seen no evidence of saturation on the connection (I appear to be on the mythical undersold node!), though it seems the complaints have been about download rather than upload. I have occasionally downloaded 200-300GB/month on both connections and received no complaints. Of course, in the real world, it's not likely to max out your download on a single file (though I have gotten about 600KB once or twice on a single torrent).