To be Marked&bloched means that you got to know a guy pretty well on facebook. You sent him naked pictures of yourself, enjoyed sexchatting and set up a date to meet him. You fly to meet this guy/gal and after the sex you realize that he/she will never talk to you again and before you even get home they have defriended and blocked you on facebook.
I just got Marked&bloched! I'm never meeting someone online again!