I've been asked this question before. Here's the MSN article on the subject. I agree that online degrees from well-known schools (the article cites Stanford), are a good bet since the curriculum is usually the same as the regular class-room based program. We (Microsoft) do tend to do a lot of recruiting from top MBA programs so I do think that if you are going to spend the time and money to get an MBA, the quality of the program should be your first concern, especially if you want to work at a top company.
When I think of the value of the MBA to a potential job seeker, I think of 2 things:
1) the skills you learn in the program that may prepare you for the type of work you would like to do
2) the fact that the MBA (especially from a really solid programs) differentiates you from the masses of other folks that could be applying for the job.
With #1, I definitely feel that there are opportunities for people to gain the same skills outside of an MBA program, through equivalent work experience. Typically, the latter is less theoretical, more practical (and of course, MBAs go on to jobs where they use their educations in practice as well). So for positions that require these specific skills, hiring managers should be willing to hire folks with or without an MBA; really focusing on the skills themselves, regardless of where they came from. With #2, there's a prestige factor associated with some schools and with the fact that you were disciplined enough to get through the program. I totally get that. And we absolutely value MBAs, just not to the exclusion of valuable work experience.
MBAs are definitely part of some of the profiles that we work on here (for example, a good percentage of management consultants and product management types that we hire come with MBAs). But I rarely think of a good recruiter searching on a specific skill-set and ruling out people who have it just because they don't have MBAs (because of the equivalent work experience thing). Many MBAs do end up with backgrounds that we typically recruit so the MBA alumni associations are a good channel for us...but the MBA itself is rarely an absolute requirement. We really look at the work experience first.
Having said that, a strong MBA on your resume does help differentiate you from others (and gives you access to some of the career services like the MBA Alumni job sites that corporations use to post jobs). Part of it is the "wow factor". So this is what you should think about if you are considering an online degree. To gain specific skills, you could get them through practical experience, so that is an option. But are you also going for the "wow" and does the program you are thinking of provide it? You have to make your own decision on which programs are "wow-worthy". An online degree from a solid program may provide the resume impact you are looking for.