ReachLocal will not effect your search engine rankings. I ran into a situation (which I blogged about) where a random SEO/SEM 'expert' told a client a recent drop in Search Rankings was an effect of ReachLocal - when it wasn't.
Let me know if you have any questions but you shouldn't be worried about using ReachLocal because of that concern. It's not valid.
I talk about the technology in detail and why you shouldn't be concerned.
[edited by: agerhart at 5:28 pm (utc) on Oct. 21, 2009] [edit reason] no URL drops [/edit]