The cloud may come with usage fees, but cloud services aren't the only ones keeping track of how much you're uploading and downloading. Many Internet service providers (ISPs) have implemented bandwidth caps, which are limits on the amount of data you're allowed to transfer over their network each month. The caps vary by provider and plan, but amounts anywhere from 100 to 250 GB per month are not uncommon. Aside from file transfers, you're using up bandwidth anytime you surf the Net, play games online or stream Netflix or Hulu videos, among other things.
Reaching your limit comes with penalties. Your provider might charge you per-gigabyte fees for whatever amount you go over the limit, throttle your bandwidth speed (i.e. slow down your connection) or even cut off your service. The latter two would definitely put a damper on your cloud upload and retrieval capabilities. And sometimes usage is capped during certain times of the day on shared networks like cable and satellite, so heavy users might experience slow-downs during peak usage times.
There are other things besides usage level that can get your data throttled, too. Many major Internet providers have begun using the Copyright Alert System to penalize people suspected of uploading copyrighted material for piracy purposes. After a few offenses, your ISP can do anything from sending you warnings to throttling your speed to blocking your service. The system reportedly monitors for uploads of known copyrighted files over peer-to-peer (P2P) file sharing software, and tracks those files based on IP address. Anyone using your service could get you into trouble, so be sure to secure your WiFi and be cautious about sharing your Internet access. However, you can get around the monitoring by masking your IP address using a virtual private network (VPN).