jgnat - You're absolutely correct, they're not very smart about targeting potential converts, and I don't think they'll ever start doing any such targeting in a way that the average JW would be aware of. What they might eventually do (if new converts are actually what they want) is start buying google ads (or having the R/F buy them and let them count them as placements or something) that target obvious keywords like bible, jesus, god, etc. But the real target will be some other things, like targeting people dealing with drug addiction (or addiction in the family), or people getting out of break-ups, or those who've just lost someone in death, etc. Targeting people who are searching for help in an emotionally traumatic time would give them a chance to get a foothold when someone's critical thinking skills have been suspended and they're susceptible to love bombing.
If they do this, I think they'll experience significant growth, at least in the near-term.
They just have to be very careful how they implement it, because the average JW strongly believes that every person (regardless of mental state, etc) deserves to get a witness, so they can't make it too obvioius that they're targeting the vulnerable only. Though, now that I'm thinking about it, it's pretty common for them to relate experiences from the platform about a householder who's well known to be rude that finally comes around after the death of a loved one. Those experiences really took on a new meaning for me once I found out how cults usually recruit, and who is most vulnerable.