I found a block when it should have taken me over 300 days, so it is possible.
Somebody wins the lottery, so it is possible to win, but that doesn't make it a worthwhile investment. Just because you won the bitcoin lottery, doesn't mean that I am likely to win.
Anyway, the amount you earn from mining in a pool is expected to be about the same amount that you will earn mining solo. It is a mistake to believe that if you earn 0.00000123 mining in a pool, that you can earn more mining solo.
The fact is that if you mine 0.00000123 BTC in a day, then the chance of finding a block each day is 0.00000123/25, or about 1 in 20 million.
http://www.youtube.com/watch?v=KX5jNnDMfxA