I ride alone (almost always), and actually prefer it. I'm not so confident in my mtb skills that I want to go all out over my head to keep up on singletrack - alone, I can do what I'm comfortable with at a pace where I don't feel like I'm going to slam into a tree at any second. Safety-wise, I don't really think about it. Like Irulan, I don't do crazy stuff (although I have had crashes where I lay there wondering if I was going to be able to get out under my own power). If you already feel unsafe due to creepies, definitely listen to your gut (I like the bear spray idea). Lots of good tips here - I should use some of them.

I don't usually even think about a cell phone when I ride. I have one - rarely use it since I don't have service at home, barely at work - more of an Ineedtopickupapizzaonmywayhome phone, or a We'regettinghomebeforekennelpickuptimemaybethey'llletusspringherearly phone. So I don't even think to ride with it. Especially mountain biking. It really would be a good idea, though.