As one who has both experience attending seminary and teaching/attending online, I would like to offer two perspectives, humbly.
1. The online experience is great, and perfectly adequate, for those in certain ministry contexts pursuing certain ministry goals.
For those who are already serving, or who are acting as pastoral interns, or missionaries, an online master's may be quite helpful. He or she will learn a lot by reading, and if she has a good online prof, will learn some from his commentary on the reading material and discussion forums.
2. The online method is not the optimal resource for the best academics.
Having done both as a student, I feel somewhat qualified to give anecdotal evidence of this. I learned a lot getting my MAR from Liberty. I really did. In fact, I thought maybe I was learning as much as those in a brick and mortar. Since I've transferred to do my MDiv at SEBTS, I've come to realize there is a marked difference in quality. Not necessarily in the books read, but in the ability to understand the material. Having a professor right in front of you virtually guarantees you will have more Q&A time than if you were online alone. While you can talk to other students and profs online, there are two issues. First, many other students are simply not theologically prepared (or maybe even not academically qualified). This is not always true, but it's enough to where it was truly a rare experience for me to learn from someone else's post (at least, by positive example). The profs often teach several sections, and take a couple days (1-2) to get back to you, usually without detailed answers (at least not as detailed as you'd get in class). As a result, even if you ask for clarification, you will do it less often and with less resolution of the issue. So, it's great for many, and it was great for me. But it will not compete at the highest levels of academics a majority of the time.