Laura,
I've done 4 JY holidays and each time I've posted numerous posts to contact others on the trip but never had many replies.
1st hol - 3 replies (18 people on hol)
2nd hol - 3 replies (45 people on hol)
3rd hol - 0 replies (35 people on hol)
4th hol - 1 reply (40 people on hol).
On all the good trips I've made good friends that i still keep in touch with, I think the community is good but not everyone uses it so dn't worry if you don't get many replies.
Mick