well in my case yes twice
not a nice feeling as it was never recipricated
if your going to then try not to talk or meet them for any thing other than that as the intimacy combined with the talking and getting to the person better could lead to you liking them more
it really depends on the person so if your easily attarcted to people and fall for people easy then best not to have one but if you feel you can have clear boundaries and keep it casual then its great
Do they actually matter?