Comcast has recently been in the news for attempting to purchase Time Warner Cable. This would be the number 1 Cable television and internet provider merging with the number 2, which seemingly violates antitrust regulations.
Currently, these companies have geographic monopolies. For example, in my city, Comcast is the only cable internet/television provider. If a consumer is unhappy with the service, he or she must switch to a different medium, e.g. satellite. If these two companies are allowed to merge, it will only further compound the issue. The new Company will be able to provide whatever quality service they want with little incentive to improve. Prices will not drop because there are no other options, and speeds/quality will not be affected either.
No good can come of the merger.