Most students I know in computer science are funded either by the NSF or their professor's startup package [in the US]. But it also isn't completely unheard of for a company to give a gift/grant to a professor to fund a student.
This seem to have a few implications, such as the student's dissertation being tied to the company's interests and the student would probably be expected to work onsite each summer.
The students I have known to do this, go on to industry after graduating (not necessarily the company that funded them). This brings up the following questions...
- Would a hiring committee at a university consider the close ties to industry a negative?
- If the student continues publishing regularly, is there anything about this scenario that can hurt one's research career?