Many students want to attend seminary online. Given how popular online education has become in the past few years, this desire is understandable. For students who have other commitments such as a career or family, attending seminary in the "virtual world" may seem like a wise move. There are both pros and cons to online courses. Having taught courses online myself (college-level, not seminary), I'm in a pretty good position to help you understand both.
The main advantage of attending seminary in an online format is its convenience. For busy professionals or those whose situation currently inhibits them from attending a traditional seminary, the convenience of attending courses anywhere using just a laptop or tablet can prove to be incredibly helpful.
The online delivery format itself has numerous other advantages, depending on how someone learns. In a traditional classroom, you often have only one chance to write down the material a professor gives the class. If you miss it, you have to either have to talk to the professor after class or ask classmates to borrow their notes. And if you miss class, it's impossible to recreate what you've missed.
In an online course, you don't have to worry about writing down the material or making sure you don't miss something - it's all there! If you're sick or have other commitments, you can schedule your classwork around your life (within limits, of course). So, with respect to learning written material (or online lectures), the online course format does have its advantages.
The biggest downside to taking classes online is the loss of a sense of community with your fellow classmates. Sure, there is indeed a community of sorts online, but it's just not the same as interacting with classmates in a real-time, face-to-face environment. There are dynamics in a classroom that are simply impossible to recreate in an online environment.
If you want to attend seminary in an online format, you have to decide if you want the online component to supplement a traditional curriculum or if you want the online courses to form a substantive component of your seminary degree, if not all of it. It's worth noting that there are only a few fully accredited seminary programs that can be completely fully online. Investigate the school carefully before you begin (and especially before you pay).
Still, there are reputable schools that allow you to complete all or part of your degree online. You will need to decide, though, if you believe these schools are a good fit for you and if the online delivery format is the best choice.