If you're looking for "raw" delivery to end-users on an international scale, then content delivery networks are probably your best choice : the big names are Akamai, Limelight, CDNetworks, Level3, ... I work for none of them, BTW.
If you're looking for additional services beyond storage and delivery, you could also look at content delivery platforms / content management systems. These typically work in ASP / SaaS mode.
Or you could build it internally, but it does get scary real quick :)
Storage & bandwidth requirements will vary a lot, depending on factors such as:
- number of assets in your catalog (obviously)
- number of video formats (mp4, wma, etc) and their parameters (resolution, audio & video bitrate)
- traffic profile : simultaneous number of connections, geographical coverage (peak hours are not the same everywhere !), etc.
- business requirements : SLA, disaster recovery, etc.