I've waited to chime in here because I didn't want to post a question and then answer it straight away. I think what makes deeperblue more of a "community" to me is the fact that it is not a local community. Here's what I mean. A local community is a group of people who have common objectives and are close enough that they can collaborate and achieve those objectives. That could be something as simple as going out for a dive tomorrow morning, or getting a petition signed to stop a particularly oppressive fish and game regulation. Spearboard is GREAT for that. But on deeperblue, the fact that you know you will probably not meet many of the other members changes the dynamic of the entire community.
In a local community you have a reputation and everything you do reflects on that reputation. Ergo, all of your actions are calculated (whether consciously or subconsciously) to protect that reputation. Therefore, when you interact with other members of a local community you are not always as true to yourself as you can be when you are with your husband/wife (who you can let your guard down around) or your close friends (who know what a dick you are and still like you anyway). But also on deeperblue, since we are primarily an online community, there is an anonymity to who we are here. Because of this, we can be whatever we want and there is really no repercussion in our every day lives. It is this fact, that we can be as selfish and obnoxious as we want without any major consequencecs, and we still decide to be helpful and friendly to eachother. We appreciate eachother more because, for the most part (at least in the beginning), we're not asking for anything other than to enjoy the company of other people with a similar passion.
Maybe it's just me, but on deeperblue I'm less guarded than I am in real life and less guarded than I am on spearboard. I love spearboard, it's got tons of great info and it's a hub off connections and contacts. But sometimes when I post on spearboard I guard my posts because I don't want people to think I'm looking for an invite on a dive trip, or an invitation to borrow some tools. While I know many of them are nice people who would be more than willing to take me out for a dive, or run me through the proper process for using a table router without earning a handicaped parking spot out of the deal, just the thought in the back of my head that I don't it to seem like I'm looking for something makes the sense of community less for me. In a sense it's the thing that makes spearboard good, that people there can really help you out in real life, that lessens the openness of the community that I think we have here on deeperblue.
--my 2 cents--
EDIT: Just for the record, I'm a pure spearo. I "freedive" primarily because I enjoy the enhanced mobility over scuba, and because it makes the sport more challenging (the fact that I'm a very mediocre freediver REALLY makes it more challenging

). I enjoy all of the freediving posts here (they helped me out a lot when I was a beginner and really brought my spearfishing to a new level) but my freediving is incidential to my spearfishing.
Another thing about deeperblue that separates deeperblue from spearboard (which is the othe forum I mentioned at the start of the thread but wasn't going to reference by name, but as that horse is out of the barn I see little point in beating around the bush now) is the maturity of the members here. While deeperblue is open to everyone of all ages, I think it reaches out to a more mature audience (not necessarily measured by age). Spearboard has a lot of members in the 13-18 age range which changes the types of posts and responses that you get. I don't mean to sound like the grumpy old man, I'm only 24, but I just enjoy the maturity that most people here share. (Disclaimer: The term maturity, as used here, specifically excludes: makin sexual jokes of a general nature; making sexual jokes that specifically pertain to Island Sands; making sexual jokes that refer to certain members sex lives (which are rich and entertaining despite the fact that their sex usually only involves one person); making jokes concerning alcoholism ranging from the casual 30 pack of beer per day to more serious drinking problems.