I do think that GMAC would be wise to anticipate that a dropped internet connection or computer crash / electricity outage is something that is likely to happen during the exam. (Though an electricity outage isn't necessarily a problem for a well-charged laptop, it would obviously sever the internet connection.) By the time my connection got dropped for the 5th or 6th time on the At-Home GRE, I realized that a wired, reliable, fast internet connection is key to maintaining your momentum on the exam, and to not having what should be a 3 or 4-hour test turn into a 5 or 6-hour slog.
With regard to cheating prevention, dropped connections / computer reboots are more of a potential problem on the GRE, where a cheater could look at all the questions, intentionally sever the internet connection or turn off the computer, solve the questions with help, then log back into the test and answer them correctly. The fact that the GMAT only lets you see one question at a time (and you can't go back) would make this less of an issue.