Following today’s dismal report from Trina Solar Ltd. (NYSE: TSL), the entire solar sector is experiencing a sell-off. The only question investors need to ask themselves is whether or not this turn of events was a surprise.

Until the first of the year, Trina and most of the other solar makers were trailing along at anywhere from down 10% to down 75% from year-ago levels. Then, as if by magic, solar stocks turned higher, and short interest declined. As of last night’s closing, SunPower Corp. (NASDAQ: SPWR) shares had more than doubled since January 2nd. LDK Solar Co. Ltd. (NYSE: LTD) was up about 24%, Yingli Green Energy Holdings Co. Ltd. (NYSE: YGE) is up more than 20%, and First Solar Inc. (NASDAQ: FSLR) was up about 6%. Only Suntech Power Holdings Co. Ltd. (NYSE: STP) had not kept pace; even Trina was up about 3% on the year.

At last count, about 30% of First Solar’s shares are held short, as are nearly 17% of SunPower’s shares. SunPower’s shares have gained the most since earlier this month, when research firm GTM Research predicted U.S. solar installation is on a steady growth path and another report indicated that new methods of financing would also help bolster solar sales.

But this sector is volatile, one might even say whimsical. Whether it’s short covering, or new investors searching for a bottom, or long-time investors who have decided to hold on until they recover at least some of their losses, solar stocks continue to trade heavily. More heavily in fact, than in those bygone days when First Solar peaked above $300 a share, nearly 10 times where it trades today.

No one can possibly think those days are coming back, ever. Right?