In the wake of the Jack Abramoff lobbying scandal, John Dickerson writes an interesting article in Slate on how lobbying really works. He explains, unlike what many people think, there is no quid pro quo. Lobbying isn't a trading cash-for-votes deal.
Instead, lobbying is a much subtler activity. The lobbyist gets access, and the legislator (or their staff) use them as a resource to understand an issue. In this way, the legislator's position can become aligned with whichever lobbyists get the access. That's why, after all, SBC has almost as many lobbyists as Texas has legislators. If it was just about cash then SBC would just need one lobbyist and a wheelbarrow. It isn't, it's about influence. Each lobbyist is a touchpoint to increase influence.
Dickerson makes clear that although Abramoff-style kickbacks are not a normal part of the lobbying process, cash is important because it buys access. I hope that when the post-Abramoff lobbying reforms happen, they may restore a little balance, so that the shallow-pocketed citizen groups will become more effective.