Dear Mr. Know-It-All I've always been proud of my scooter's great gas mileage. But a friend tells me its emissions make it no greener than a Chevy. Have I been deluding myself?

Your use of the word always implies that your scooter is rather aged. If that's the case, then your contrarian pal may be right. Older scooters with two-stroke engines emit far more smoggy pollutants per mile than their four-wheeled counterparts. True, you probably get double the fuel economy of a Chevy and can thus crow about your ride's smaller carbon footprint (and thus smaller contribution to climate change). But your tailpipe may also be belching out 10 to 15 times more smog (nitrogen oxide and hydrocarbons) than that Chevy, to the severe detriment of your city's air quality.

If you switched to a new, four-stroke scooter, you could pop your eco-jersey a bit more. New federal regulations on two-wheeler emissions kicked in for the 2006 model year, and they're slated to get even tougher for 2010. Look for a scooter with a catalytic converter — the emissions-scrubbing gizmos aren't required, but they are becoming more common.

My 10-year-old son wants to go trick-or-treating as Niko Bellic, the murderous antihero of Grand Theft Auto IV. Should I let him?

Your son's familiarity with Bellic indicates that he's an experienced GTA IV player. So if you put the kibosh on his costume, you're sending a mixed message — it's OK to play GTA but not to dress up as one of the characters.

If you're not prepared to bar Junior from exploring Liberty City, then a compromise may be in order. Let him don Bellic's gangster gear and (faux) facial hair, but strictly forbid the use of toy weapons — or any other pointy accessories, for that matter.

Granted, there's something distasteful about having your grade-schooler dress up as a drug-dealing, prostitute-beating, human-smuggling thug. But ask yourself: Is a werewolf or witch really morally superior? At least Bellic exhibits brief flickers of doubt about his chosen path. Werewolves, by contrast, never hesitate before eviscerating their prey.

Illustration: Christoph Niemann My ex-girlfriend recently posted one of my gooey love notes on her blog. I'd rather the world didn't know that I used to refer to this vindictive harpy as "babycakes." Can I compel her to delete the letter?

No doubt you intended your handwritten sweet nothings for babycakes' eyes only. But privacy, alas, just ain't what it used to be. If you claim copyright on that letter, your blogging former lover can argue that she's merely engaging in fair use. And odds are that most judges would take her side.

Your primary problem is that, by handing over the letter in the first place, you essentially published your writing — not in the conventional sense, perhaps, but in the eyes of the law. "When boyfriend gave the letter to girlfriend, he transferred ownership of the letter to the girlfriend," says Marc J. Randazza, an Orlando attorney and law professor who blogs at The Legal Satyricon. "This transfer of ownership is akin to you buying a book or magazine. That transfer, I think, is a publication, even though it was to just one person." So consider yourself a published writer. (Congratulations!)

Unfortunately for you, it's a lot harder for a plaintiff to win a fair-use argument when the work in question is published. According to Ned Snow, a professor at the University of Arkansas School of Law, courts that mull such cases are primarily concerned with whether the use impairs the market value of your work — be it letter, drawing, or photograph. You'd probably have a tough time convincing a judge that you intended to turn that love note into cash — especially since you presumably didn't keep a copy for yourself.

Courts can be fickle, of course, and you could pull off a miraculous upset. But do you really want to go to the mat on this one? The embarrassment seems minor, and steering clear of vengeful exes is always advisable. If it makes you feel any better, Mr. Know-It-All once fondly referred to a paramour as "peanut." You're certainly not alone.

Need help navigating life in the 21st century? Email us at mrknowitall@wiredmag.com.