Should I tell him she's cheating on him?

[Chloe]

I have this friend Austin. We used to be best friends but now not so much. He is talking to (not dating) this girl. She also used to be one of my good friends. On twitter her and this other guy are talking and flirting and favoriting eachothers tweets. She retweets him a lot. They tweet about hanging out stuff like "I had fun last night" and tag eachother.

Then my friend Austin is oblivious to this. He is crazy about this girl and he really likes her. He always tweets about her and she favorites but doesn't retweet. I don't think she likes him a lot and everyone thinks Austin is her second choice. This happened last month too and then he went back to talking to her.

Do I tell Austin that u think she is talking to someone else or do I just let him figure out himself?

[Jamey]

What do you gain from telling him (if you're not best friends?) He would have to be extremely thick not to know what you know already (especially if it's public on twitter). If you tell him, he may just say 'yes I know don't state the bloody obvious'. It is none of your business, really.