I believe that social games should be allowed; we've had several questions on them already, they seem to have gone over well. There is also some overlap between social games (or party or parlour games), and board games, so it would be hard to draw an exact dividing line.
I'm less sure about pervasive games; I'm not terribly familiar with them, so if you could write or link to a good definition of them, that would help. What I'm writing here is based on a very rough idea of what they are from a little bit of Googling and glancing at some information.
I think that some of them might be on topic, while some are closer to sports, RPGs, or computer games, which are off-topic. Essentially, I would say for pervasive games, if social interaction, strategic skill, and random chance (dice, cards, RPS) are the bulk of the game, they could probably be considered on-topic, like Werewolf or the social aspects of Diplomacy (which also has a board, so that helps).
If there's a significant physical aspect or geographic aspect (as in some Assasin's games or geocaching), it may be off topic; better for a dedicated pervasive games forum, or possibly considered a sport. If there's a substantial roleplaying aspect, or LARP like aspects, it might be more appropriate for a roleplaying forum. If there's a considerable online aspect like Alternate Reality Games, a computer gaming forum could be more appropriate.
I think that we should generally try to be inclusive if possible here; try not to close anything as off topic if it could be considered on topic. However, there's a certain aspect of "I'll know it when I see it."
We can also try and apply the rules of thumb that I listed in another answer about what's on topic; "playable on or around a table" may have to be stretched a little, but Diplomacy already stretches that (as you need to be able to go off and make and discuss alliances in secret, so a substantial portion of the game is not around the table). I think a guideline for what is acceptable is that only social interactions may be taking place elsewhere than on or around a table; if there are substantial physical components beyond that, you're rapidly approaching something different than what we cover here.
For reference, the rules of thumb I listed:
- Be playable on or around a table
- Have objective rules of play and win conditions
- Offer dynamic challenges, either through other players, randomization, or both
- Be playable by hand, by human players implementing all of the rules