I don't mind giving advice to people I don't know if I have the time, what really burns my canoles is when a friend/family commits me to helping someone else (eg "Oh come on, it'll take a few minutes and they're such nice people").

True story, a lady dentist friend of the wife asked for help once, I helped no problem. After a couple hours to clean up her husbands pron dialers and malware from said pron sites (I don't judge), I gave a rundown on what to watch out for, hooked her up with free versions of antivirus and antimalware, the usual stuff. No biggie.
Then a few months later, my daughter got her braces caught and caused some damage. Wife takes her to the lady dentist friend to look at it, ok sounds great. The dentist took less than 20 minutes to fix the problem (just needed to reseat the wire, not as bad as it looked). This was a slow day - no business lost fitting us in. No materials needed. Get a bill for 100 - for a few minutes work that cost nothing in materials.

Lady dentist on the phone the other night, "oh noes I can't open word, can you come over and fix? urgent, ahh". Yeah, that's gonna happen. Seriously?!?