lol, zigzag told you right...as far it goes on the surface. A bit deeper, it could also mean someone is diametrically opposed to your "general bearing" or specific message(s)...so they want to be able to quickly find your posts and offer a differing opinion.
But, yeah, in general, it shows you've piqued someone's interest, for whatever reason. Lottsa times, peeps are marked cuz they seem to make the earliest calls on potential runners, ie, a "momo play."
Or, maybe you follow certain topics: the person marking you figures they can monitor your posts easier than trying to monitor that topic...
Anyway, no, zig's right, it ain't a bad thang...
But, then, it ain't a bad thang to have few marks, either. Some very good, brilliant posters may have relatively few while some mainly pumper types have a gazillion.
It's like any other "club": after awhile you get to recognize that some have "a following" for one reason and others have a following for completely different reasons...