I have been in an on-again-off-agin relationship with a man for the past two years, prior to that we lived together for a year. A month ago we were suppose to hang out, but he called to say that he was hanging with his buds that day and could we reschedule. I said cool, email me during the week and we will figure something out. A month later and nothing. I text him on sat. about something random and funny, but he never responded. I am assuming that he maybe seeing someone... I wasn't born yesterday to know the signs and yesterday was his birthday and I didn't wish him one... and that is not the issue... the issue is that he would leave me hanging... after three years you would think that there would be a little respect there, yes?

You would think that after three years there would be a little respect or at the very least an explanation.
Can you be certain nothing has happened to him?
Perhaps in these tough financial times he did not pay for his internet.
Its easy to jump to conclusions but there could be viable reasons for no contact.
I would try calling and asking if everything is O.K. because there is always the possibility that all is not.

The question is here is "why do you care"? He has no obligation to you nor do you have any to him. So go and live your life and stop worrying about things that you shouldn't.

Sounds like he took the cowards way out of breaking it off with you completely. Be happy you will never have to deal with him and his cowardly ways again.

If the girl I like didn't respect me, it would be pretty easy for me to forget her.

Why insist on liking someone who don't respect you?

This is the cowards way out, you do deserve an explanation but frankly I don't think you need it. He's a coward -( there is your explanation)
Just be thankful you didn't get all the crappy excuses.

Don't assume, just be unavailable for a while.