121.5 has one use, one use only and should be kept clear. If anyone is too ill disciplined to abide by that the problem is theirs. Surely you're not telling me that the need to chat to your mate, colleague or whatever is SO pressing that you have to break the rules? Get a grip. You're at work as a so-called professional. Act like it.
As for the 'On guard' calls, why not? If someone is mistakenly calling their company or whatever and fails to realise their mistake (I heard someone make four calls yesterday in a vain attempt at ordering a wheelchair on landing) someone needs to tell them otherwise the frequency may not be clear when someone needs it the most.