And the point is ?
The web shield is an active scanner and during activity (and shortly after) memory use will be elevated. Windows up to a point controls RAM and when to hand back some of it, RAM is there to be used and for most people70MB is a drop in the ocean.
I have many applications that use more and do less, Firefox, SnagIt Editor, explorer.exe, svchost.exe, acs.exe, Snagit32.exe and ashServ.exe on my system right now use more memory than ashWebSv.exe, am I woried about them either, no, I have 2GB of RAM and it is there to be used.
It also depends on what memory measure you are using, there are several columns in the task manager. It also depends on what you are doing and how intensive the browsing activity.