EDIT-YES, stealing power would be my new #1!
#1-Other knowing about your grow(jealous or angry friend/customer gets busted/gossip gets to wrong ears/ect.)
#2-Not taking care of odor issues(use carbon filters)
#3-Police or fire dept response to home for other reasons then the grow--tied--landlord or maintenance person coming in
#4-Neighbor reporting suspicious activity at your home
#5-Delivery person(USPS/UPS/FEDEX) reporting suspicious packages delivered to home
#6-Disgarding evidence in trash without securing it
#7-Using local grow shops especially in smaller cities near you
The very last and least threat to getting busted, even though it's pushed as a common threat is excessive electrical use. Most power companies do not flag excessive use to find people who are growing pot, they flag to investigate possible theft. Electrical consumption needs to be drastically high or regular use needs to have made a drastic change in order to be flagged at all, and most flags are just a phone call rather then an investigation. By drastic I mean A LOT. If say your electrical/gas bill is 50 a month it can go to 200-300 without being flagged, I don't know the threshold but it most cases it been 10X the regular use to be flagged and investigated, so to be safe don't exceed 5X normal use. Fact is, most power companies tend to flag accounts who drastically drop electrical or gas use rather then use more. Unless you are already being investigated for related activities your electric bill is the least of your worries. There are so many reasons and devices one could use legally that would raise electric rates high. The key is to have multiple rooms with multiple lights running on different light schedules rather then having all your lights running at the same time. Instead of having one large flower room have two smaller ones running on opposite schedules. If one flower runs 6am-6pm have the other running 6pm to 6am. With veg that's tougher but most veg rooms should be nowhere near the wattage of your flower room. And the installation of smart meters, which is only currently about 10% of the nation, are mainly used to help the customer get better rates and help the company to charge higher rates depending on time of use, they are not meant to monitor your activity and no meters can monitor how you use your electricity.
I'm out in the middle of nowhere now in a med legal state and mostly off grid power(diesel and solar) for my electricity but even when I was in the city, in both a home and an apartment, I never worried about electrical use. Only case to worry would be if you rent and the bill is not in your name or you have free utilities, this means in most cases the landlord sees the monthly statement every month and any changes would be noticed immediately by them.
