I've always felt this is one of the big obstacles to growing this hobby. Some big plusses to local shops:
1) No shipping charges
2) No shipping hassles - Ever had something new with an issue and dealt with returning via the mail? The cost, the hassles, the time wasted...Don't have this problem with a good local shop
3) Can test an item before you take home or they can test it for you before shipping
4) If you don't live close by and you ask they will probably bring with them if displaying at a show (or maybe they belong to a modular club which runs at several local shows a year).
5) Can provide valuable advice on making a layout or graduating to the next level in the hobby
To me the above is worth forgoing a discount.
Local shops need not be local. My local hobby shop stopped carrying the brand I primarily collect due in part to the reasons stated in this thread. This forum lead me to another local hobby shop who provided all the services I listed above.
To those of you who wish to save a much as possible and deal with stores without a brick and mortar presence I wish you the best of luck. Just beware that many have policies in place which are decided NOT customer friendly.
Plus you never know who you might meet and possibly meet new friends in the hobby.
--Greg