I've long complained about internet data caps. While I haven't yet exceeded Comcast's 250GB cap, I noticed a blog post retweeted across Twitter with a real-life anecdote of one person's experience getting cut off from Comcast internet service for doing just that. link
In his case, service was likely* due to an increase in uploading large files to cloud services that are becoming more and more popular. My own usage is still primarily downloading data (above 95% of my monthly use is downloading); but as we have new Windows 7 smartphones that automatically upload pictures to the Skydrive service, and the upcoming Mango update promises to do the same with HD videos as well, I can see uploading rates increasing for me as well.
*"Likely", because Comcast does not provide details about data usage, even to show how much is up- vs. downloading.
I do find it odd that, instead of charging for overages and milking more money out of their customers, they are throwing customers away. I imagine there are users who would much rather pay extra than being cut off completely. And yet, they are effectively reducing their customer base, which will only shrink more as more people go over the cap by daring to use all these internet services other companies are so keen in innovating, which will only happen more often when Comcast refuses to increase the cap proportionally to how many services are available, the increase in bandwidth existing services use (i.e. more HD video available for streaming), and the increasing speed Comcast itself is providing to get to their arbitrary cap faster.