Reverse splits are usually when the stock price drops so low it's in danger of getting delisted.
BVSN is the prime example, It was around 6-8, moved up to 250+ and had a 3:1 split, so the price became 80-ish. And moved back up to the same area and had another 3:1 split. When the reality began to sink in(Incidentally, BVSN peaked when it was announced it was going in the S&P500.) As it sold down, the price falling horrendously, they had a 1:9 reverse split. Giving back the two 3:1 splits... And later, as it continued sinking, they had a 1:25 split.
So, if you had 100 shares in September, 1999, the next month it was 300 shares...then a few months later(March 1999), another split, and you had 900 shares. 2 years of selling off, and in July, 2002, a 1:9 reverse split and you were back to 100 shares.. That didn't work either, and in October, 2008, a 1:25 split and you had 4 shares. So, suppose you bought in late '98 at $10 a share, you spent $1000. Right after the first split, the stock was at 100, you had 300 shares, you thousand dollars was now worth $30,000. If you held on a little while, a couple days before the second split, BVSN topped at 250ish your thousand dollar investment was now $75,000. The second split came, but it was after the top. Fast forward to July, 2002, you now are back to 100 shares...but they're only worth about $250 bucks. So, you hold and hope...in October, 2008, the final indignity...1:25 reverse split, you only have 4 shares...total value...$40. That's right.
So, that's about that when it comes to splits and reverse splits. Reverse splits means the company isn't doing very well.