Speed, skills and cost are the three things that first come to my mind.
Speed: depending on location, students may have access to high speed internet, allowing for more efficient use of video interaction or downloading larger files. But on the opposite end, people who are not in an area with access to broadband are limited to dial-up internet, hence they miss out on take full advantage of on-line learning.
Skills: students who have had adequate experience in computers and internet prior to starting a course that involves on-line learning will have beneficial advantage over those students who are computer literate. Hopefully, with the modern education system, this will become less of a problem.
Cost: the cost of high speed internet is still relatively high. So students who are on low incomes may not be able to afford it and have to rely on cheaper but slower connection. This brings us back to “speed” that I pointed out above.