It is common for dating sites to offer features that let you spy a little on the activity of another user, like seeing who viewed your profile or read a message you sent.  I call these spy features.  Here’s a full list of the ones I’ve encountered:

1. “Who Viewed Me”: Usually sites will let you do this only if you opt to be seen as well.  We’re all curious as to who is checking us out but is it worth it?  Not everyone who reads your profile may be interested, and not every interested person will leave your profile and still be interested.  It may also inhibit people from looking at profiles because they’ll be noticed.
2. See if sent message was read: This feature exists really just to see when a message was read.  So what is its purpose besides helping you be a stalker?  Sometimes I read a message but don’t have time to respond.  The other person could make a wrong assumption if they decided to check up on me.
3. See who “favorited” you: Some sites let you add people to a Favorites list, but on Match.com you can find out if you’re on someone else’s list.  I like the idea of having this list but it should definitely be private!

Are there any more?  Is there any value to these kinds of features?  Have they helped you before to get a date?