I used to be, in my opinion, overcautious about abstaining from any contest like that to keep full rights to my photos ... but I guess I eventually started to feel like I was just hoarding a load of photos that no one would ever see and no one wanted anyway. So now I'm much more lax about throwing photos out here and there when the opportunity presents itself.
And it's working out a lot better for me, I've gotten a good deal of exposure and even some € from doing so, and I feel better about myself. I tell myself "so what if I'm giving this photo away, I can take much better photos and plenty of them"
I'm not suggesting not being careful, I'm just saying enjoy this exposure while you have it. You keep getting your name and your photos out there like this and soon everyone who is anyone will be throwing the likes of a "GoIreland" calendar aside and buying the "Layla Kurper 2014" instead. :-)
Anyways, mine is just the opinion of a nobody whom I'm sure doesn't know any better.