In the position I'm looking into (the client has already told the recruiter they want me), I would be contracted to a company that coordinates my schedule for their client. Compensation would be as a 1099 Independent Contractor.
Unlike a doctor, lawyer, Accountant; I wouldn't have my own business unless the S-Corporatio or LLC made sense. This is what I'm looking into now.
As far as liability...in theory, I suppose the client (of the agency I'm contracted to) could sue me if I made a costly mistake. Something to consider, I suppose...but I don't see liability as being a big threat in the kind of work I do.
Although I've done a lot of contract work over the years, this would be the first time I'd be going in as 1099 (although it's not unusual for this type of engineering work). Previously, I'd work as a "short term" (W-2) employee of the contracting agency.
Many large companies use contractors. I know Harley Davidson's engineering dept. was about 40% contractors. This is advantegeous to the contractor as it frequently pays a higher rate and to the company as they have less "employees" on the books.
This kind of work also depends on the quality of the contracting agency (not the client). Some have been around for years and are good to work with. Due to the crappy economy, there's a lot of upstarts (both in contracting and recruiting) that really suck. That's why it's important to actually interview with the client company to make sure it's a good fit (not all are...I could name one that was very recent).
Bottom line is, can I do this job and make money at it.