Serving in a Church you wouldn't attend?

9Marks have an interesting post on working in a church you wouldn't otherwise attend.
This is interesting to me 'cause I've been involved in helping in youth work at a church that I actually left and many friends have or still do serve in different capacities at churches that they don't go to and wouldn't attend.
Now I know the 9mark post is talking primarily about taking a wage and job at such a church, however I think the principle can be carried to voluntary service at other churches in serving in their youth clubs, goodnews clubs etc.

Any thoughts on this? [If you wouldn't attend a church, why or why not would you serve at it?]