Is it a good idea to name some model attributes (and table columns) by prefixing _id to it? For example, an application will collect some transaction ID. transaction_id would be a good name for it, but it will not be associated to any other table. What kind of bad doodoo would this cause?
As long as it's not used in any model relationships i don't see any trouble it could cause.
I can't think of any problems this would cause, but it will likely confuse the heck out of the next developer on the project...