Microsoft Lync Server 2010 supports both DNS load balanced and hardware load balanced solutions. While DNS load balancing can be used to distribute SIP traffic equally among the various Front End servers in a Front End pool, a hardware load balancer must be used to handle HTTP connections to Lync Web Services. Please note that a hardware load balancer is not required when a Lync Server 2010 Standard Edition or a single Lync Server 2010 Enterprise Edition Front End Server is deployed within a Lync environment.
Read more at source: http://blogs.technet.com/b/nexthop/archive/2011/11/03/hardware-load-balancer-requirements-for-lync-server-2010.aspx
Cheers,
Anderson Patricio
http://blogs.msexchange.org/patricio
Twitter: @apatricio