Well, this joke act thing is surely as much a product of the voting for Ed as it is for the show constructing his comic journey. I can sit and watch an awful dancer, but I won't vote for him or her because it just doesn't move me and I see no point wasting a vote on something that doesn't make me love dance. The first two dances tend to be fine as it helps that celeb break the dancing ice and connect very quickly to an audience (in a contrasting way that good dancers will), but then the problem after is the show and couple know what works for them and tend to stick with it till it wears thin Plenty will vote for say Ed (or types like him), which is fine, we all vote for what we want and should do, but I do feel sorry at times for 'joke' acts when their fans keep voting them and they feel obliged at times to keep playing the fool as that is their selling point/survival skill for staying in the show. Of course in fairness, some Ed fans may want to see a serious side, but it can be hard to break a mould, esp as even if you try and attempt to be serious it can still can out comical (if it tends to just be the way you dance and are and it's stuck in the minds of those automatically associating certain expectations of you).
There is also the argument that Ed (and types like him) at times may enjoy it as well as feel embarrassed by it, I'm sure there are contrasting feelings from the 'joke' acts. Ed does seems pretty enthusiastic and prob does want to be seen serious at times but things don't always come out intended and mistaken comedy occurs (like with the lift, it was prob meant to trump Greg and Natalie's as a showpiece, but just went wrong. If had gone right, there may have been the right type of praise for his attempts instead of what did come as a result of it going wrong).