I held off on handling this because James and I were thinking about artificially limiting the number of custom parameters a user can store. SqlLite doesn't enforce text storage limits (which is how we're storing custom fields), but we're going to be doing that very soon. In the meantime our documentation says to use the feature responsibly. It's not a very used feature on AppBlade yet (since it's not a very useful one there yet), so we aren't expecting a problem.