The simple fact remains that the door-to-door work the JWs participate in is got to be one of the most ineffetive, gross time wasters ever embarked upon. Look at the # of hours spent per each convert (I haven't done this recently, but do some searches on this board, the numbers are astronomically high). The only reason it's still done is a) it's free for the WTBTS as they use slave labor to accomplish it, and b) it's an effetive tool for taking up yet more of a JWs little remaining time each week, thus keeping them busy in 'make work' so they cannot have time to begin to question their belief structure. Of course, those number are probably a bit off since I bet most JWs are a bit 'generous' when they fill out their monthly 'hey I'm spiritual after all' report card.
Fact is, most other religions are growing faster than JWs, and they do little to no door to door activity, at least in the mannar that JWs do. They do however, participate in community activities, advertise in papers/radio/tv, mail flyers, and do charity work. Among other things. These require more $$ commitment from the church itself, thus the reason you would never see JWs doing that (unless they start to get desperate due to falling #'s of converts).
I find it hard to beleive that a loving god would consider this an effective means of preaching his word to the world. Especially when that message is 'join us or you will die' (and your little dog too! <insert cackle>)