I've shot a number of NHL games in Dallas from the stands. The confusing thing to me was the difference in the rules printed in the program distributed at the venue and the rules on the Dallas Stars website. I'll be honest and will say I can't remember which said what, but one said it was okay, the other not.
I ended up figuring that the worst that could happen is that I'd have to schlep my backpack out to the car, so I showed up with a 1D something and a 70-200 2.8 and a 100-400. The security guy had me open my backpack, looked in, and let me through. So I think this varies by venue/organization.
While I know that organizations like the PGA (which I've read has one of the most stringent/protective rulesets about usage of images of PGA Pros) are at one extreme, I figure the NHL was sort of at the other end - looking to rebuild fan support after the lockout a few years back - so if folks show up and take some pics to post online - more power to em... I think the main issue would be what would happen if I had tried to sell those images, especially for commercial (non editorial) usage.
As a photographer that does quite a bit of work with Professional Cycling, I know more about what that "environment" is like. Yes, the advent of dslrs, cell phones w/ good quality cameras, etc - has broadened the number of photogs who can get scenics and other venue shots - there is still a premium paid to those who can get on a motorcycle as a part of the race. At most large races (Tour of California or USA Pro Cycling Challenge in Colorado) the race organization provides about 10 motorcycles w/ drivers who have been "vetted" and know the rules as to where and when they can be in a race. Then, media submit requests for time on the motos and it usually turns out that 4 or 5 get rides for the full week. These are photographers who have "agency" or big cycling publication contracts. The rest of the motos are apportioned by need and by city. So local media get a shot for a day, while other freelance shooters who have other agreements with teams or sponsors can get a day or more on a moto.
That gives us a better opportunity to get more shots from a day's racing, giving us the "critical" images that others just can't get. We're still fairly limited as to what we do with them. We've a fairly wide berth on usage in editorial situations - media outlets, websites, blogs focused on racing; the teams buy some, etc. The athletes themselves have varying levels of sensitivity to sale of their image for commercial usage. They are also fairly okay with sale to fans for personal display/use... so some money can come in from print sales via a website. Usually they are okay with a team or personal sponsor paying for images, but random other products who want to insinuate that say Lance Armstrong has endorsed their product, not so much. Having shot for a number of top teams, I'm sure that I've received repeat business because I've not abused the privelege...
I think I'd sum this up as follows - it can never hurt to ask a team/venue/whatever about getting access. The worst they can say is "no" - but I'd just also be cognisent of what you want to do with the images and be up front with said venue. They'll let you know if there is an existing contract, etc. As another example, there is a velodrome near my old house in Dallas, TX. I was the "track photographer" out there for about 3 years or so. The track organizers and officials were nice enough to chat with other photogs who showed up to shoot. If they were on "assignment" for a rider or a sponsor or local news - no worries; but they asked that the shooters respect that I was there for every race and to not post images for general sale. Could the shooters still sell? sure - but I think all of them didn't - as there is a bit of a code of ethics between shooters. I did see a few post images for sale and I never emailed or called anyone about it. I guess part of it was that there wasn't that much money in velodrome sales... <chuckle> I was doing it to support the sport and the venue.
Hope that helps - sorry if I rambled a bit.