If you want to buy on line, buy on line. If you want to buy @ your local store, buy @ you're local store. Do what makes you happy, and will make you happy at the end of the day.
A good business foundation and structure as well as back up business plans for when times boom or are tough, are essential in all businesses including the scuba diving industry. If one does not possess these plans one will never succeed no matter how many people buy things off them.
I buy online for the simply reason it is cheaper, much cheaper. Eg Mares extreme reg in Australia $1495 AUD, on Scuba Toys/Leisure Pro $650-700 USD, even when converted is still less and it is not a special order which I assume means you order it and we will ship it into the country. This happened years ago when I bought a Mares isotherm semi dry wet suit which actually took 8 weeks to arrive as it had to be made/come from Italy.
If you are lucky to have a wonderful LDS go for it. I have many around here but they do not have the gear I want, Mares, and it is all special order and buying gear down here is very expensive.
I live in an area where lots of dive stores come and go. 18 months is the average and the Sydney region itself has an extremely high amount of dive stores for not alot of divers.
I also do not have the luxury larger countries eg USA, Uk etc have when it comes to choosing gear. We have a very small market which is not as larger as others therefore instead of 10 BCD's to choose from there are only 2-3 offered. This to me does make a difference.
As Matt from Fort Myers said, you have a great LDS like he is at go for it and support them, I am actually interested in diving the one he mentions next time I am in Florida because he says it is so good.
Why support a dive store or any store for that matter that doesn't support you but at the same time one must consider more than just price alone. Service, people, deals. People make the difference I believe.
People say only buy @ your local store, but if your LDS is coming into the computer age they should be expanding their business model to include the Internet in some way.
I travel alot for work and take my gear with me all the time, and the way I choose a dive store I wish to dive with from renting tanks/weights/dm or instructor guide/boat or shore dives is off their Internet site. This tells the picture & story for the person 5000 miles away who wants to use their services.
To who suggested bring more people into the sport, this is a great idea and one that will keep the sport growing.