Generally speaking, how bad of an idea is it to go "car camping" alone?

Good idea. Just leave details of your trip back home with someone you trust: your camp location and when they should expect you back. I'm sure it's not without its risks, but I've gone car camping and backpacking many times as a single female with no issues.

Good idea. Don't worry. Just go! (tell somebody where you are going and when you expect to be back).

I have done this. I've also backpacked alone many miles from anybody. Mostly it's boring once you've set up camp and you're alone for the night. If you're the type to get spooked over every noise you hear, there's that too. As others have said, take general safety precautions. Make sure someone knows where you are. A whistle around your neck is probably more useful than a cell phone in that situation. Usually campgrounds, at least in the busy season, have caretakers who will roam around at night, collect fees, and generally keep an eye on things. In bear country most established sites have bear boxes for food, or they just advise you to keep stuff in your car. Most of the other animals are harmless, unless you hit a moose on the road. I once had a fox steal my Tevas though. I found one about 100 yards away and the other maybe 100 feet beyond that. It is my generally feeling that one is safer alone in the woods than they are walking around an average American town at night, at least in terms of worrying about dangerous people. This is just my feeling though, I have no actual data to back it up.

Thanks everyone! I'm thinking to start out at established campgrounds where you pay a fee - I've done this a handful of times with others so thats where my comfort level is - and will ressearch and talk to campground staff when planning my trip. I know there's no way to be 100% safe with anything you do, but I don't like to live my life in fear...I'm happy to read all your advice and to see that there are others (especially womena) out there who don't think it's such a bad idea afterall.

Don't lock your keys in your car.

I'm a middle-aged female person, and I just went on a Road Trip, car camped in national and state parks, and slept in the minivan in lots of urban and other locations. I made sure I knew where the keyfob and its alarm button was, and never had occasion to use it, except for turning off the alarm when the car thought I shouldn't have opened the locked door. I've learned that one can get http://www.tailveil.com/s http://www.factorychryslerparts.com/products/gb/DODGE/RAM-Cargo-Van/Tent/4397993/82209878.html?partner=googlebase_adwordsAccessory&kwd=&origin=pla go on the http://www.ebay.com/bhp/minivan-tentback http://www.amazon.com/exec/obidos/ASIN/B004G6U3J2/metafilter-20/ref=nosim/ of a http://www.autoaccessoriesgarage.com/Truck-Tents/Sportz-Minivan-SUV-Tent or http://www.rei.com/product/851616/?cm_mmc=cse_PLA-_-pla-_-product-_-8516160002&sportz-suv-4-tent,-blue/grey/black&preferredSku=8516160002&mr:trackingCode=65ECAC7D-7021-E311-A755-BC305BF82162&mr:referralID=NA&mr:device=c&mr:adType=pla&mr:ad=44272128160&mr:keyword=&mr:match=&mr:filter=61471045600&msid=MIWAUZTK_dc%7Cpcrid%7C44272128160%7C&%7Bcopy:s_kwcid%7Dback, and http://www.amazon.com/exec/obidos/ASIN/B000ENOBVW/metafilter-20/ref=nosim/ I want to make one.

Did it a lot as a female traveling alone even staying in rest areas and not just campsites. General precautionary measures - make sure someone knows where you are more or less and when you'll be back - make sure you have a cell phone charged and handy - bring spare food/water/warm clothes - YMMV about this but if I was camping near my car I don't think I'd lock my car in case I needed to get into it in a hurry - pay attention to your spidey sense and feel okay moving on if something or someone seems weird or off - whistle and other good first aid emergency stuff which you should bring if you're alone or with someone - pay close attention to the weather because in the northeast it can change quick - consider carrying a GPS of some kind with you if you go out on long hikes

Yeah, put me in the Very Good Idea camp. If you're nervous about criminals I would start out going to places like state parks that have busy, well-populated campgrounds, instead of places like state/national forests where you'd be more isolated.

I'd feel quite safe camping alone at any state or national park campground, which is what I picture when you say "car camping."