This probably doesn't happen to everyone, but I was asked to level a mage if I wanted a raid slot in my guild. Of course, I had myself to blame for this as much as anyone since I tried to regain my status in my old guild and turned my back on a group of people I had grown to love. In the end, however, I learned a valuable lesson and now love being a mage.
It started out when my current guild fizzled out late in BC. We were a 25 man raiding guild that stalled in Tier 5 content. After many unsuccessful attempts to revive our guild, we simply gave up and planned on rebuilding for WotLK.
During this time I regained contact with my old friends and spent a lot of time with them, and less time with my guild mates. After a bit of time I moved most of my alts into my old guild, leaving only my warrior in my raiding guild. As you can imagine after the hours of raiding with my warrior, I didn't spend a whole lot of time on him.
After the expansion I had originally planned on changing my main to hunter and leveled that first, but found far too many other hunters at 80 within days. I immediately leveled my warlock to 80 shortly after, simply because she was my money maker and disenchanter. After that I decided I needed a new main character.
I turned to Shaman and leveled that to 80 within a week. I wanted to be elemental as I didn't want to be a healer or melee dps and went that path to raid with my old guild. This was a rough time for elemental shaman as the DPS was way below par. They pretty much axed me from the main group one day quoting the bad dps (which was not much below many of the others), so I left the guild with all of my characters.
I started playing my warrior again, hoping to get my raid spot back here, and hit 80 in a hurry. The problem is that they were solid on tanks and needed dps. I did some raiding with my shaman here in the short term, but they asked me to level my mage ASAP and I could go back with them.
The next week was spent hurriedly leveling my mage to 80, and I did it in record time. Took me about four days from level 70. From there they rapidly geared me up in some heroics and did my first mage raid a few days after.