It may had been in the past during the times when many Slavic countries were gaining independence. I don't see pan-Slavism as an instent to control more land, although some politicians may use the ideology to fulfill their political agenda.Slavs have plenty of land!

Well the people who fear Pan-Slavism aren't afraid of Slavs being friendlier to each other, they're just afraid that Slavs will use that cooperation to work together to take land.

Excuse my arrogance but wtf is 'Greater Albania'?

You might know it as 'Ethnic Albania', both names are used.