In a recent game I was down to me and one other race. I knew I was not going to win culturally or militarily which left tech. However, the other race was also ahead of me technologically (they were researching beyond human and I was 2-3 tech's behind them. What was holding me back was a large military I had kept to get the evils off my back. Now that they were gone I had a lot of excess spending. So what I did was sell all of my ships except 3-4 rangers to the one remaining race for 1500bc (everything in their bank) over 30 months. I then cranked my tech spending to the max and took off. A few turns later they were like 66000bc in the red, they couldn't research anything. Their military plus tribute was strangling them. Sure, they demanded some money from me (I would accept every 2-3 times to keep them from declaring war) but in the end I won a tech victory. woot woot.
This kind of tactic would be more necessary however once the Xpack is out as there is a new rule that humans will not be able to win via tech if the AI reaches FF first. In 1.05, there is no tech race per se as you could still win a tech victory even if the AI completes the tech tree before you.