John Mayer and Jennifer Aniston were spotted out together a third time after having apparently having lunch and dinner and spending the night together at Aniston’s hotel on Friday in South Beach, Miami. OK! Magazine reports that they were seen having dinner on Sunday, so maybe we can assume that they spent the weekend together and that those are the times they were seen out.

OK! also says that “friends” of Mayer’s are warning Aniston that he is a charmer who hits it and quits it, and that she should watch out for herself, because he has a history of making girls swoon over him and then pulling away. He is said to have been relentless in pursuing Jessica Simpson, but to have quickly grown tired of her:

But the 39-year-old actress may want to be cautious about this potential beau. Friends of the 30-year-old Grammy-winner say he has a long track record for leaving women heartbroken. “Girls fall for him hard because he’s charming,” one friend tells OK!, “but he has a reputation for crushing the girls he’s with.”

Jessica Simpson and actresses Minka Kelly and Jennifer Love Hewitt are just a few women who have been wooed by John.

“He came on so strong at first,” a pal of Jessica reveals to OK!. “He wanted to be with her every moment. When he wasn’t physically with her, he was texting her — but all of a sudden, he got bored and stopped returning her calls.”

[From OK! Magazine]

John Mayer is arguably attractive. He’s not my type, but a lot of women like the dark brooding type and he’s certainly a talented musician. What I want to know is how anyone can stand being around him for an extended period of time. He seems like such a self-absorbed talker that he would bug the shit out of even the most patient women. Still, Mayer must have something that these beautiful successful women find attractive.

In an excruciatingly long interview with Best Life Magazine, Mayer revealed that he worries about what the girl of his dreams “thinks when she reads about me in US Weekly.” Jennifer Aniston also has a whole public persona invented and perpetuated by the tabloids, and they must be able to relate to each other incredibly well on that issue. Perhaps Mayer is a better listener than you would assume, and it’s possible Aniston is willing to listen to him ad nauseum, because they have a lot in common. Maybe they’ll find some solace in each other and last as a couple. You can sort of see them working despite Mayer’s history.

Jennifer Aniston is shown in a new ad for Smartwater, thanks to Splash. John Mayer is shown at Scleroderma Research Foundation’s Cool Comedy event on 4/16/08, thanks to WENN.