This really depends on your reasons for wanting to do it. Consider it like this: If there is a security issue, would your database be more secure by using a more restrictive account in some places and a less restrictive account in others?
I think that this would actually only add complexity to your project. Having two accounts would be just about the same as only having one user account unless you never planned on accessing anything but the read only account from your ASP pages. If you plan on updating or inserting into your table you will need the less restrictive account, and at that point you have placed your self in the same situation as you would be in with a single account. If this is a security issue than it's possible someone may have a more specific or better answer to your concern, but I hope my previous remarks help.
-Tarwn The three most dangerous things in the world are a programmer with a soldering iron, a hardware type with a program patch, and a user with an idea
-computer saying (Wiz Biz - Rick Cook)