Lobbies are a double sided knife. On one side, they can shape the government´s policies to facilitate business for certain part of the private sector; on the other, there will always be doubts about the opacity and corruption involved.
When I moved to the US in 2014 lobbying was an unknown territory for me. They were not regulated in Spain and most of lobbying activities happened under the radar of the public. However, Spain has proposed to regulate them and I think it is a very good move.
Lobbying in the US is one the most developed practices and there are a lot of companies and people involved in it (including law firms), specially in Washington, and the public generally accepts it.
Wikipedia defines "Lobbying" as "the act of attempting to influence the actions, policies, or decisions of officials in their daily life, most often legislators or members of regulatory agencies".
Like I mentioned earlier in the post, a lot of questions arise when you realize what they do: whose interest are they trying to protect? how do they do this? do legislators receive anything in return?
There is a lot of suspicion about lobbying. There is an evident conflict of interest between the companies pushing for legislative change and the constituency that elected the politician. Additionally, this activity almost always occur in closed meeting rooms that leave no trace of what happened in there.
However, there can be positive effects of lobbying. Small interest groups can join together and cause legislative change, or even bigger interest groups can meet with the policy makers and help them make informed changes in the policies.
My view is that, although very controversial, a very transparent, well regulated lobbying practice is very beneficial for a country. There is always a two-sided dispute for every policy change, having lobbyist from opposite interest making their points, which will ultimately make the politicians make more informed decisions that will (hopefully) benefit the citizens. The key is to have the interests of the governments, private sector and the citizens aligned.