I do it because it's amusing.

I'm a spontaneous person. One tells me he/she loves me and I'll go awww, i love you too.
There is this person that is a friend of my sister's and this particular person professes his love for me which i think is rather hilarious.
He'd keep saying that he's serious albeit we've never met face-to-face and we've talked on the phone once and IMed.
I've known him for a year but we've never really had conversations until recently.
is it normal to find it amusing to go along with it? And is it normal to not take it seriously?