I always try to stay IC, GM event or not. I took part in some GM events, never got a reward. The following example shows my (evil) char's behaviour during one event.
(21:11:42) >Cleaning Kran raises an arm and points towards Orgonwukh.
(21:11:47) Cleaning says: I clean armor?
(21:12:13) Orgonwukh frowns "Don't touch my armor, mate. I can handle that myself."
(21:12:22) Cleaning says: Yes ser
(21:12:32) Cleaning looks at Orgonwukh, as if waiting for a tip
(21:12:53) Orgonwukh chuckles "What now?"
(21:12:56) Izzabella smirks
(21:13:05) Cleaning stares at Orgonwukh
(21:13:38) Orgonwukh looks at Cleaning "Not very bright, eh?"
[...]
(21:17:15) Anonymous says: I have a battle hammer to be cleaned. How many tria do you take for that?
(21:17:32) Cleaning turns to Zwenze "2 coins only!"
(21:18:01) Anonymous nods and gives cleaning a Battlle hammer and two circles
(21:18:33) Cleaning looks at the circles and frowns "No give me bad money"
(21:19:24) Cleaning says: I only green coins
(21:19:29) Cleaning says: Gold coins not want
(21:19:38) Orgonwukh bursts out laughing
(21:19:57) Orgonwukh says: You can give those gold coins to me, kran. I give you two green for one gold coin, eh?
I left this event when the cleaning kran said he was hungry and about 30 guys were running and brining him various meals, crystals and ores to eat.
As I said, I never got any reward from any GM event I took part. So I have two choices:
1. Stay IC and get frustrated because of the OOC behaviour of other players. And in the end I get no reward for my RP, but they get some for whatever they did.
2. Avoid GM events as some of you have already proposed.I tried 1. for a long time, but in the end I ended up with 2.
I know it requires a lot of work and patience to set those events up and I do not want to complain only here. So my only proposal is to not reward players anymore with items or money. Maybe there could be something like a 'roleplay fraction'. You could reward participants for their roleplay efforts. Maybe this fraction could be visible to everyone, so if I look at someone's description, I could easily recognise people who have proved that they know how to roleplay nicely. People maybe would try to improve that fraction to get respect from other players and by giving negative points for OOC behaviour, we could also identify 'black sheep'.
Oh, there might be another solution for me:
3. Create a 'goodie goodie' alt and log him when I regognise an event is running 
... reconsidering... No, because:
It's good to be bad 