I've done it 3x for people associated w/my church or another nonprofit. Unfortunately it has been not a fully satisfying experience in any case. (I wanted to be a little less involved in it...more an angel....but have never been able to work it out that way).

First time, was offering a guy ATL-LON-NBO, but couldn't get the ticket to work out (he wanted to go with a group, and they'd bought ATL-LGW on DL connecting LHR-NBO on BA. Did find him a free LHR-NBO ticket to match theirs, and he had miles (as I recall) to get to London, but BA gave him hassle at LHR and kept him off the flight as they investigated...they did put him on the evening flight. Bitter taste one.

Second was a simple Houston-ATL to meet some specific timings over a weekend. I was able to get a IAH-ATL-HOU routing pretty easily, but the guy was flaky and a bit of a poophead ("I don't care about which airport I go out of" converted to "HOW CAN YOU POSSIBLY EXPECT ME TO GO OUT OF ONE AIRPORT AND INTO ANOTHER") ...fine, go pound sand, dude.

Third worked out reasonably well. DTW to Bucharest this summer. Stopover anywhere is desirable. No luck with Skyteam. Was able to find a good DTW-ORD-LHR-MUC-OTP-VIE-LHR-IAD-DTW connection on UA/LH/Austrian for 50K with 23 hours in LHR on the way out. Confirmed it with recipient, who called UA and was able to catch it before ticketing (paper ticket needed) and add several more days in LHR on the way out which worked out well for all concerned. Kudos to UA Dearborn call center.