Liability?

I host two rides each year, a one-day in May and a two-day in July (which was just this past weekend). In both cases, they're characterized as group workouts with a published route. No entry fee, no sag. For the May ride we gather at a local watering hole after for beer and burgers. For the July ride I provide beer and snacks (sandwiches) after the first day's ride. If I were to charge any kind of fee, even if it were for the food, I'd be opening up a huge door for liability. I have everyone sign a standard waiver before we take off each day. It's a slightly modified USAC waiver (my mod is in the drug statement, changed to say that "I'm not on any substance that will impede my ability to safely do this event."

I post them publicly on Facebook, and discussions go from there.

I would think that including a swim without some kind of monitoring/lifeguard could open up some additional liability, but I'm no expert. Conversely, providing support that's not certified could be worse.

The short answer is yes.  

If you invite friends over to watch a ball game on TV, your liability increases (but maybe not much).  

If you invite friends over to swim or boat, your liability increases (more than a televised game), maybe a lot more.  

If you invite friends over to ride open public roads, your liability increases (probably less than swimming boating).  

If money changes hands, your liability increases A LOT because you're now offering fee-for-service.  

McFuzz is spot on. Your duty to your guests depends on the relationship. If friends, it's lower. If customers, it's higher. Regardless, there is still some level of potential liability. Make sure you have good insurance, and if you are really concerned, you could ask your friends to sign a waiver.