The give away could have been the warmer temperatures. The buds on the dogwoods. The leaves waving in the breezes. The longer hours of daylight. The allergy-induced sneezes around the office.
The give away could also be, though, the philanthropic opportunities that abound. When the temperatures rise, so do the number of walks and races. Many employees enjoy participating in these events, which can present a problem for employers who have non-solicitation policies. You don't want to quell the well-placed intentions of the employees. Almost everyone can find an organization to support who has one of these physical fundraisers. Yet you also know that some organizations can be more controversial than others. Controversy aside, some employees feel tapped out by the time spring gets here, what with the cookie, popcorn, candy, wrapping paper, pizza kits, stationary, and calendar sales that dominate the fall and winter months.
For some employers, the easy way to address this is to completely bar these events--no posters, no e-mails, no flyers in the kitchen, etc. Others take the approach that only employer-sponsored events can be solicited, and those are usually done indirectly (such as by e-mail or by posting something without any fanfare). Still others have a free-for-all, seeing these activities as a way to build employee friendships and cooperation.
Whatever your approach, as always, ensure that it complies with your non-solicitation policy. If you don't have one of those policies, then take care to see that you have some type of objective criteria (written or no) that provides guidance on when you do allow for solicitation and when it is prohibited.
Happy running/walking! (We have to figure out some way to work off those cookie, popcorn, candy, and pizza pounds, don't we?)